The Dive Profile (a graphical representation of the depth of the dive as a function of time) is shown in the panel on the top right hand of the Subsurface window. When a dive is manually added to a logbook, Subsurface presents a default dive profile that needs to be modified to best represent the dive described:

Modifying the dive profile: When the cursor is moved around the dive profile, its position is shown by two right-angled red lines as seen below. The time and depth represented by the cursor are indicated at the top of the black information box (@ and D). The units (metric/imperial) on the axes are determined by the Preference settings. The dive profile itself comprises several line segments demarcated by waypoints (white dots on the profile, as shown above). The default dive depth is 15 m. If the dive depth was 20 m then you need to drag the appropriate waypoints downward to 20 m. To add a waypoint, double-click on any line segment. To move an additional waypoint, drag it. Moving can also be done by selecting the waypoint and using the arrow keys. To remove a waypoint, right-click on it and choose "Remove this point" from the context menu. Drag the waypoints to represent an accurate time duration for the dive. Below is a dive profile for a dive to 20 m for 30 min, followed by a 5 minute safety stop at 5 m.

Specifying the gas composition: The gas composition used is indicated along the line segments of the dive profile. This defaults to the first gas mixture specified in the Equipment tab, which was air in the case of the profile above. The gas mixtures of segments of the dive profile can be changed by right-clicking on the particular waypoint and selecting the appropriate gas from the context menu. Changing the gas for a waypoint affects the gas shown in the segment to the right of that waypoint. Note that only the gases defined in the Equipment tab appear in the context menu (see image below).

With the profile now defined, more details must be added to have a fuller record of the dive. To do this, the Notes and the Equipment tabs on the top left hand of the Subsurface window should be used. Click on this link for instructions on how to use these tabs.

The use of dive computers allows the collection of a large amount of information about each dive, e.g. a detailed record of depth, duration, rates of ascent/descent and of gas partial pressures. Subsurface can capture this information, using dive details from a wide range of dive computers. The latest list of supported dive computers can be found at: Supported dive computers.

To import dive information from a dive computer to a computer with Subsurface, the two pieces of equipment must communicate with one another. This involves setting up the communications port (or mount point) of the computer with Subsurface that communicates with the dive computer. To set up this communication, users need to find the appropriate information to instruct Subsurface where and how to import the dive information. Appendix A provides the technical information to help the user achieve this for different operating systems and Appendix B has dive computer specific information.

After this, the dive computer can be hooked up to the user’s PC using these steps:

Dive computers tend to keep a certain number of dives in memory, even though these dives have already been imported to Subsurface. For that reason, if the dive computer allows this, Subsurface only imports dives that have not been downloaded before. This makes the download process faster on most dive computers and also saves battery power of the dive computer (at least for those not charging while connected via USB).

Bluetooth is becoming a more common way of communication between dive computers and Subsurface. Subsurface provides a largely operating system independent Bluetooth interface. An increasing number of dive computers use Bluetooth Low Energy (BTLE) as a means of communication. However, BTLE is not a standardized protocol, consequently adaptations need to be made for communicating with each different dive computer model. See the list of supported dive computers. Bluetooth communication is often more reliable if all Bluetooth devices seen by the Subsurface computer are removed and pairing with the Bluetooth dive computer is performed from afresh. The Bluetooth and BTLE interfaces are under active development with respect to new dive computers that use these mechanisms of communication.

Setting up Subsurface for Bluetooth communication requires four steps:

Select the Download dialog by selecting Import → Import from dive computer from the Main Menu. After checking the box labelled "Choose Bluetooth download mode", the dialog below appears.

Although the Subsurface Bluetooth interface is intended to function without Bluetooth pairing at the operating system level, it is always prudent to follow up initial Bluetooth pairing problems by pairing the Bluetooth dive computer with the Subsurface computer using the operating system services of the desktop computer. Delete all existing pairings and start by scanning for Bluetooth devices from an empty list (on the desktop) of Bluetooth devices. Once Subsurface has recognized the Bluetooth dive computer, subsequent divelog downloads are likely to be simple.

On the Linux or MacOS platforms the name of the Subsurface computer and its Bluetooth address are shown on the right hand side. The power state (on/off) of the Bluetooth adapter is shown below the address and can be changed by checking the Turn on/off box. If the Bluetooth address is not shown, then Subsurface does not see the local Bluetooth device. Ensure the Bluetooth driver is installed correctly on the Subsurface computer and check if it can be used by other Bluetooth utilities like bluetoothctl or bluemoon. This completes the first two steps above. Ensure the Bluetooth-enabled dive computer is in PC-upload mode and it is discoverable by other Bluetooth devices. Consult the manual of the dive computer for more information. Now the third item in the list above has been finished. Select the Scan button towards the bottom left of the dialog above. After searching, the dive computer should be listed (perhaps as one of a number of Bluetooth devices) in the main list box on the left-hand side of the dialog (see image above). If this does not work, select the Clear button, then scan again for Bluetooth devices using the Scan button. After taking these actions Subsurface should see the dive computer. On the left hand side, if the computer has more than one local Bluetooth devices connected, use the list box to indicate which one needs to connect to Subsurface. The label of the discovered dive computer contains the name of the device, its address and its pairing status. For BTLE devices the address often starts with "LE". If the device is not paired and has a red background color, a context menu can be opened by selecting the item with a right-click. Select the Pair option and wait for the task to complete. If necessary, consult the user manual of the dive computer being used. This accomplishes steps 4 and 5, above.

After the devices are paired, press the Save button of the dialog. This closes the Bluetooth dialog. Now select Download in the Download from dive computer dialog which should still be open. The downloaded dives are shown on the right-hand side of the download dialog.

It may be necessary to distinguish between different dive computers used to upload dive logs to Subsurface. For instance if a buddy’s dive computer is the same make and model as your own and dive logs are uploaded from both dive computers to the same Subsurface computer, then you might like to call one "Alice’s Suunto D4" and the other "Bob’s Suunto D4". Alternatively, consider a technical diver who dives with two or more dive computers of the same model, the logs of both (or all) being uploaded. In this case it might be prudent to call one of them "Suunto D4 (1)" and another "Suunto D4 (2)".

To achieve this, display a dive downloaded from this dive computer, right click on its name in the profile and select the option to set a new nickname. If this option isn’t shown, then Subsurface cannot reliably identify this specific dive computer (not all models support this feature, but most modern ones do).

Some divers use more than one dive computer at the same time, e.g. during technical diving. If you import the dive profiles from these different dive computers into Subsurface, the profiles can be viewed independently. During upload the data from the dive computers are automatically merged into a single dive. The different profiles are presented on the Profile panel with the name of each dive computer indicated at the bottom left as well as an indicator of the number of dive computers uploaded for this dive (e.g."No. 2 of 2"). The original dive profile is shown by default while profiles from additional dive computers are added "behind" that of the first uploaded dive computer. While the dive is highlighted in the Dive List, switch between the profiles of the different dive computers by using the left/right arrow keyboard keys. If profiles from more than one dive computer exists for a dive, right-clicking on the name of the dive computer (bottom left of the profile panel) activates a context menu (image below) that allows one to make the selected dive computer the one whose profile is shown by default: this changes the order in which the profiles are shown when using the left-arrow and right-arrow keys. The context menu also allows deleting any of the dive computers or to take the information from a specific dive computer and present that as a separate dive.

The data in the Notes panel are not affected by the specific dive computer that is selected.

With the uploaded dives in the Dive List, the information from the dive computer is not complete and more details must be added to have a full record of the dives. To do this, the Notes, Equipment and Information tabs on the top left hand of the Subsurface window should be used. These three tabs represent a increase in the amount of information stored for a dive.

METHOD 1: After downloading dives from a dive computer, the dive profiles of each is shown in the Dive profile tab, as well as a few items of information in the Notes tab (e.g. water temperature) and in the Equipment tab (e.g. gas pressures and gas composition). Other fields remain empty. It may be useful to simultaneously edit some of the fields in the Notes and Equipment tabs. For instance, it’s possible that a diver performed several dives during a single day, using identical equipment at the same dive site, or with the same dive guide and/or buddy or tags. Instead of completing the information for each dive separately, select all the dives for that day in the Dive List and insert the same information in the Notes and Equipment fields that need identical information. This is done by editing the dive notes or the equipment for any one of the selected dives.

Simultaneous editing only works with fields that do not already contain information. This means if some fields have been edited for a particular dive among the selected dives, these are not changed while editing the dives simultaneously. Technically, the rule for editing several dives simultaneously is: if the data field being edited contains exactly the same information for all the dives that have been selected, the new, edited information is substituted for all the selected dives. Otherwise only the edited dive is changed, even though several dives have been selected in the Dive List. This speeds up the completion of the dive log after several similar dives.

METHOD 2:There is a different way of achieving the same goal. Select a dive with all the appropriate information typed into the Notes and Equipment tabs. Then, from the main menu, select Log → Copy dive components. A box is presented with a selection of check boxes for most of the fields in the Notes and Equipment tabs. Select the fields to be copied from the currently selected dive, then select OK. Now, in the Dive List, select the dives into which this information is to be pasted. Then, from the main menu, select Log → Paste dive components. All the selected dives now contain the data initially selected in the original source dive log.

Many divers wish to annotate dives with text that indicate particular events, e.g. "Saw dolphins", or "Released surface buoy". This is easily done:

The information entered in the Notes tab and the Equipment tab can be saved by using the two buttons on the top right hand of the Notes tab. If the Apply changes button is clicked, the dive data are saved in the memory image of the dive. If the Discard changes button is clicked, the newly entered dive data are erased from the computer memory, although the dive profile is retained. When the user exits Subsurface there is a final prompt to confirm the new data should now be saved permanently on the computer disk.

Importing dives from other software is done through a universal interface activated by selecting Import from the Main Menu, then clicking on Import Log Files to bring up dialog A, below. The exact appearance of this dialog differs between operating systems.

Towards the bottom right is a dropdown selector with a default label of Dive Log Files which accesses different types of direct imports available, as in dialog B, above. Currently these are:

Selecting the appropriate format from the dropdown list and then the specific log file in the main window containing the file list. Then select the Open button near the bottom right.

If the dive log being imported is in CSV format, the user is given the opportunity to perform manual edits to the column headers before it is imported to Subsurface (see image below).

For more information on configuring a CSV import, see Importing data in CSV format. In many cases changes to the column headers are not required because they are pre-configured for the specific type of import and the CSV import screen can be bypassed by selecting the OK button. This opens the imported dive log in the Subsurface Dive List.

Some other formats not accessible through the Import dialog are also supported, as explained below.

OSTC Tools is a Microsoft-based suite of dive download and dive management tools for the OSTC family of dive computers. OSTC Tools downloads dive data from the dive computer and stores it as a binary file with file extension .dive . Subsurface can directly import these files when using the universal import dialog. From the dropdown list at the bottom right select OSTCTools Files (.dive .DIVE). This makes the OSTC Tools dive logs visible in the file list panel. Select one or more dive, then click the Open button. The OSTC dives are shown in the Dive List panel.

All H&W devices supported by OSTCTools can be imported to Subsurface. This includes OSTC, OSTC Mk2, OSTC 2N/2C, OSTC3, OSTC Sport, and probably although untested, Frog, OSTC2 and OSTC CR.

Please remember that OSTCTools is not true diving log software, but rather a useful set of tools for analysis and management of OSTC devices. Only raw dive computer data will be imported to Subsurface; the rest of the data (buddies, equipment, notes, etc) need to be completed manually.

Since Mares uses proprietary Windows software not compatible with multi-platform applications, these dive logs cannot be directly imported into Subsurface. Mares dive logs need to be imported using a three-step process, using www.divelogs.de as a gateway to extract the dive log information.

SmartTrak stores the raw data from a Uwatec/Scubapro dive computer along with a plethora of other data manually added by the user, ranging from dive points to buddies data or DAN survey info. However, this is Microsoft Windows-based proprietary software by Uwatec (today Scubapro) using Microsoft Access databases, preventing the integration the importer into the Subsurface core application.

A stand alone tool for Linux has been developed to import the .slg files generated by SmartTrak to Subsurface’s .xml format. It can be downloaded from the usual Subsurface repository, as a Windows installer or a Linux AppImage. The application is not currently supported on Mac.

It can also be built for Linux systems. Two dependencies need to be met in your system before building: glib2.0 and mdbtools (see below).

In addition, a web service is available for divelog conversions from SmartTrak to Subsurface (see below).

Feel free to contact the Subsurface development team on our mailing list for assistance in importing SmartTrak dive logs.

Importing dive information from divelogs.de is simple, using a single dialog box. The Import → Import from Divelogs.de option should be selected from the Main Menu. This brings up a dialog box (see image A below). Enter a user-ID and password for divelogs.de and then select the Download button. Download from divelogs.de starts immediately, displaying a progress bar in the dialog box. At the end of the download, the success status is shown (see image B, below). The Apply button should then be selected, after which the imported dives appear in the Subsurface Dive List panel.

Subsurface can directly import the database generated by the proprietary SeacSync application. Simply locate the database file on your computer, then use the universal import dialog.

On Windows 10, The SeacSync database is typically found in: C:\[USERNAME]\AppData\Roaming\SeacSync\divesDB.db

Subsurface will not modify the database during import, so it can be imported directly from this location.

A comma-separated file (.csv) can be used to import dive information either as dive profiles (as in the case of the APD Inspiration and Evolution closed circuit rebreathers) or as dive metadata (in case the user keeps dive data in a spreadsheet). The CSV format is a universal simplified format that allows easy information exchange between different computers or software packages. For an introduction to CSV-formatted files see A Diver’s Introduction To CSV Files. Subsurface dive logs can also be exported in CSV format to other software that reads this format. See APPENDIX D: Exporting a spreadsheet to CSV format for information that may be helpful for importing spreadsheet-based data into Subsurface.

At the top right of the dive site management panel is a text box (see image above). If you wish to only show dives from a particular site, then type a partial dive site name such as "Genova". This shows only the dive sites that have been described for Genova, assuming that the word "Genova" forms part of the dive site name or description.

The information for each dive site can be edited either from from within the Notes tab or within the Dive sites tab. In order to edit the dive site information, select the Edit icon to the left of the dive site name (see image above). Editing dive site information from within the Notes tab is discussed in the section on Locations where each of the fields in the dive site edit panel is explained.

Add any desirable information to the tab. Editing of coordinates is explained in the section dealing with Locations. Having finished editing the dive site information, select the Done button at the top. This returns you to the dive sites management panel.

Merging two or more dives is achieved in the dive site edit panel (see image above). We assume that the dive sites that need merging are not far apart. Merging is performed by selecting a dive site and then merging other dives with this selected dive site. In the edit panel, above, select the text box labelled "Show dive sites in the range of:" and provide a critical distance that would include the site that needs to be merged with the present site. A list of sites within this range is presented (see image below).

Select the dive site to be merged by right-clicking it. A confirmation message is presented (see image above). Clicking the confirmation message merges the selected dive with the dive named at the top of the panel and returns you to the dive sites management panel.

Alternatively, if exactly one dive site is selected in the Near dive sites list, there is an additional function Merge current site into this site available in the context menu. This can be helpful if the name of the destination dive site is not known, e.g. when importing dive sites from a third party source.

At the top right of the dive sites management table is a round button with a "+". Clicking that button inserts a new site entitled "New dive site" into the list (image below). The new site can also be deleted (maybe after erroneously clicking the + icon or you realized the dive site already exists) by selecting Edit → Undo from the main menu or by typing Ctrl-Z (or CMD-Z on a Mac) while the dive sites management table has focus. Edit this new site by selecting its edit icon and provide a name, coordinates and, if preferred, a description. Clicking the "Done" button in the edit panel returns you to the dive sites management panel.

On the left of each dive site is a dustbin icon. Clicking the dustbin deletes that site. If there are any dives performed at that site, a warning message is shown (see image below). If this site is then deleted, the location(s) of dives that used this site would need to be created.

Since the dive sites list is managed separately from the dive list, it is possible to add dive sites to the list even though these sites have not been used for any dives. In this case the column labelled "# of dives" shows a zero. This makes it possible for divers to share dive sites and sites can be created before any of them are dived. Alternatively a site can be created with a useful description such as "Ann dived this site last summer and she saw huge numbers of bumphead parrotfish. She said Jan - Apr is the best time. I hope to dive there myself". In this way the dive sites list becomes a repository of useful information outside of the dive list.

At the top left of the dive sites management panel is a button "Purge unused dive sites". Selecting this button deletes all the dive sites that do not have associated dives.

Right-click on a dive or on a group of dives on the dive list, bringing up the Dive list context Menu. Select the appropriate option to import media either from file or from the Internet. The system file browser appears. Select the folder and media that need to be loaded into Subsurface and click the Open button. Towards the bottom of the file browser is a filter that allows showing media (photos and videos), only photographs, only videos, or all files. Choose the appropriate option.

If media are imported from the Internet, provide a URL pointing to a single media. If the URL points to a directory, no images are imported: images from the Internet need to be imported one at a time. If media are loaded from the Internet, Subsurface assumes there is an Internet connection each time this item is viewed within Subsurface.

Having selected the local folder or Internet image to be imported, the time synchronization dialog appears (see image below). The time synchronization is not perfect between the dive computer used during a dive and the camera used during that same dive. These two devices often differ by several minutes. Subsurface attempts to synchronize them so that the exact times of media can be used to position media on the dive profile.

Subsurface synchronizes camera with dive computer in three ways:

If the timestamp of a photograph or video is more than 30 minutes before or after the dive, it is not placed on the dive profile (see the red warning in the image above). However, If the appropriate checkbox is selected (see image above) these images can still be placed on the Media tab of the Notes panel so that all media associated with a dive are visible, including images taken before or after the dive.

After the media have been loaded, they appear in two places:

This results in a profile display as in the image below:

Hover the mouse over any of the media stubs. A thumbnail image is shown of the appropriate media. See the image below:

Clicking on the thumbnail brings up a full size photo or video overlaid on the Subsurface window, allowing a good view of the media (see the image below). Note that the thumbnail on the dive profile has a small dustbin icon in the bottom right hand corner (see image above). Selecting the dustbin removes the image from the dive. Be careful when clicking on a thumbnail. Images can also be deleted using the Media tab (see text below).

Media associated with a dive are shown as thumbnails in the Media tab of the Notes Panel. Media taken in rapid succession during a dive (therefore sometimes with large overlap on the dive profile) can easily be accessed in the Media tab. This tab serves as a tool for individually accessing the media of a dive, while the stubs on the dive profile show when during a dive when a photo/video was taken. The size of the thumbnails in the Media tab can be changed using the Zoom level slider at the bottom of the panel. Single-click a thumbnail in the Media panel to select a photo/video. Double-click a thumbnail to view the full-sized image or play the video, overlaying the Subsurface window. Delete media from the Media panel by selecting it (single-click) and then by pressing the Del key on the keyboard. This removes it BOTH from the Media tab as well as the dive profile.

By right-clicking on a video and selecting the "Save dive data as subtitles" option, a subtitles file with the same name as the video but with an ".ass" extension is created that contains time dependent dive data (runtime, depth, temperature, NDL, TTS, surface GF) to be overlayed with the video. The VLC video player automatically finds this file upon playing the video and overlays the dive data. Alternatively, the ffmpeg video encoder can be used to create a new video file with the dive data encoded in the video stream. To do so run

from the command line. You need to have the libass library installed.

Most underwater photographers store media on an external drive. If such a drive can be mapped by the operating system (almost always the case) the media can be directly accessed by Subsurface. This eases the interaction between Subsurface and an external repository of media. When associating a dive profile with media from an external drive, the normal procedure of selection and synchronization (see text above) is used. After the external drive has been disconnected, Subsurface cannot access these media any more. If the display of media is activated (using the toolbox icon to the left of the Dive Profile), the program shows only the thumbnails and the images cannot be viewed at full-screen size. If the external drive with the media is re-connected, the media can be seen in the normal way.

Inspecting each individual dive in order to determine whether there are associated media can be time consuming. There is a rapid way of seeing which dives have associated media and which not: activate the Media checkbox in the dropdown list obtained by right-clicking on the header bar of the Divelist. In the Divelist, all dives with associated media have an icon indicating whether the media were taken during the dive, just before/after the dive or both during and before/after the dive. More information is provided in the section dealing with photo icons on the Divelist.

After a photograph or video has been loaded into Subsurface and associated with a specific dive, Subsurface saves the path to the directory where the media lie as well as the file name of the each photo/video, in order to find it when the dive is opened again. If the media or the whole media collection is moved to another drive or to a different machine, the path to the media changes. Now, Subsurface looks for the photos/videos at their original location before they were moved, cannot find them and cannot display them. Because, after moving media, large numbers of files may need to be deleted and re-imported from the new disk, Subsurface can locate the media based on their filename and path.

This is done by selecting from the Main Menu: File → Find moved images. This brings up a window within which the searching of the images can be controlled. The search is started by clicking on Select folder and scan. Since recorded during different dive trips might have the same filename, the names of the parent folders are likewise compared. Therefore, the root folder of the NEW picture collection should be chosen. For finer control, it is possible to search only for media of the currently selected dive(s) by selecting the appropriate option.

After the searching has completed, the original filenames and the new locations of the photographs will be shown. The matching parts of the paths are emphasized. Media that are found at their known positions are not listed. The proposed changes can be applied by clicking Apply or rejected by clicking Cancel.

Subsurface easily handles dives involving more than one cylinder. Multi-cylinder diving usually happens (a) if a diver doesn’t have enough gas for the complete dive in a single cylinder; (b) if a diver needs more than one gas mixture because of the depth or the decompression needs of the dive. For this reason multi-cylinder dives are often used by technical divers who dive deep or long. As far as Subsurface is concerned, there are only two types of information that need to be provided:

When this is complete, Subsurface indicates the appropriate use of cylinders in the dive profile. Below is a two-cylinder dive, starting off with EAN28, then changing cylinders to EAN50 after 26 minutes for decompression.

Several dive computers perform automatic recording of cylinder pressure. In this case no manual intervention is needed. Older dive computers (e.g. Uwatec Galileo, several Suunto models) handle more than one pressure transducer on cylinders, switching from one sensor to another as the diver switches among cylinders and providing a sequential record of cylinders pressures during a dive. Some of the latest models (e.g. Shearwater Perdix AI, Scubapro G2) record two or more pressure transducers concurrently and continuously during the whole dive. In these cases Suburface correctly interprets the data. There is continuous effort within the _Subsurface development team to add new dive computer models to those that can be downloaded from and to represent cylinder pressures correctly. Regardless of the type of sensor handling of dive computers, technical divers are likely to use both automated and manual methods of cylinder pressure logging when more than two gases are used. However, automated recording of cylinder pressure simplifies logging of sidemount dives (where two cylinders are used). See the list of supported dive computers.

Sidemount diving is just another form of multi-cylinder diving, often with both or all cylinders having the same gas mixture. Although it’s a popular configuration for cave divers, sidemount diving can be done by recreational divers who have completed the appropriate training. See the comments in the last paragraph, above, about automated recording of cylinder pressures. Manual logging of cylinder pressures during sidemount involves three steps, exactly as with multi-cylinder dives above:

When importing a dive Subsurface generally has to make some assumptions when importing dives. One of these assumptions is which cylinder a pressure sensor is attached to. The following dive is a sidemount dive with two deco cylinders. Each of the main cylinders has a pressure sensor attached to them. In this case Subsurface only knows about 3 gasses and 2 sensors so it makes the assumption that the sensors are attached to the first two cylinders, one bottom gas and one with deco gas. For the cylinders with attached sensors the cylinder index will be shown in the sensors column.

To fix this, you can add a new cylinder with bottom gas and pick the index for the deco cylinder in the sensors drop down.

After this change the second sensor will be attached to the fourth cylinder and the two deco cylinders won’t have any cylinders attached.

The profile graph will also be updated to reflect this change.

To log pSCR dives, no special procedures are required. Use the normal steps outlined above:

In pSCR diving, the inspired gas often has a pO₂ below that of the fresh gas from cylinder. This is because fresh gas is only supplied at a slow rate and the diver continuously uses oxygen from the loop for metabolism, resulting in the so-called "pO₂ drop over the mouthpiece". For pSCR dive profiles the dive ceiling is adjusted for this oxygen drop, and often requires longer decompression periods. Below is a dive profile of a pSCR dive using EAN36 as bottom gas and oxygen for decompression. Note that this dive lasted over two hours.

Visualizing the pO₂ drop_: The difference between the pO₂ of the fresh cylinder gas and the pO₂ in the loop can be visualized in Subsurface by opening the Tech setup panel in the File → Preferences menu item and then providing suitable information in the section labelled pSCR options. The pSCR metabolic rate is your rate of oxygen metabolism in liters/min (commonly between 0.5 and 2.5). The Dilution ratio is the ratio indicating how much gas in the loop is replaced with fresh gas, relative to the gas being breathed (common values are between 1:3 and 1:10). These values are also used when planning pSCR dives. If the oxygen content of the loop is not recorded by an oxygen sensor, Subsurface estimates the pO₂ in the loop using the information supplied above. This pO₂ is shown as the green line representing the oxygen partial pressure in the dive profile. If the oxygen pressure in the loop is measured using an oxygen sensor connected to a dive computer, this information is probably recorded by the dive computer and these measured pO₂ values are shown on the dive profile. In addition, the Tech setup Preferences panel allows one to activate a checkbox labelled Show equivalent OC pO₂ with pSCR pO₂. This activates display of the pO₂ in the fresh gas from the cylinder (an orange line). The vertical distance between the orange graph and the green graph indicates the "pO₂ drop over the mouthpiece". Much of pSCR diving involves managing this pO₂ difference.

The Information box displays a large range of information about the dive profile. Normally the Information Box is located to the top left of the Dive Profile panel. The Information Box can be moved around in the Dive Profile panel by click-dragging it with the mouse so that it is not obstructing important detail. The position of the Information Box is saved and used again during subsequent dive analyses.

When the mouse points inside the Dive Profile panel, the information box expands and shows many data items. In this situation, the data reflect the time point along the dive profile shown by the mouse cursor (see right-hand part of figure (B) above where the Information Box reflects the situation at the position of the cursor [arrow] in that image). Moving the cursor horizontally lets the Information Box show information for any point along the dive profile. It gives extensive statistics about depth, gas and ceiling characteristics of the particular dive. These include: Time period into the dive (indicated by a @), depth, cylinder pressure (P), temperature, ascent/descent rate, surface air consumption (SAC), oxygen partial pressure, maximum operating depth, equivalent air depth (EAD), equivalent narcotic depth (END), equivalent air density depth (EADD, also as gas density in g/l), decompression requirements at that instant in time (Deco), the surface GF (a measure of inert gas loading of the diver’s body defined as the excess over the surface pressure normalized such that the maximally allowed over pressure at the surface, the M-value, corresponds to 100%), the time to surface (TTS), the calculated ceiling, as well as of the statistics in the Information Box, shown as four buttons on the left of the profile panel. These are:

If at some point a isobaric counter diffusion situation is encountered in the leading tissue (defined to be a moment in time where helium is off-gassing while nitrogen is on-gassing and the net effect is on-gassing) this is indicated in the infobox as well. Note that this condition not only depends on the gas that is currently breathed but on the tissue loadings as well.

Figure (B) above shows an information box with a nearly complete set of data.

Many dive computers record events during a dive. For instance, most dive computers report alarms relating to high partial pressures of oxygen, to rapid ascents or the exceeding of no-deco limits (NDL). On the other hand, other events are classified as warnings and, for instance, occur when the remaining gas in a cylinder falls below a predetermined limit, a deep stop needs to be performed or the need to change gas during multi-cylinder dives. Some dive computers also report notifications, e.g. when a safety stop is initiated or terminated or when a predetermined amount of OTUs have been incurred. The alarms, warnings and notifications differs from one dive computer to another: some dive computers do not report any of the above events, while others provide an extensive log of events. The reporting of events is therefore a function of the dive computer used. In addition, Subsurface does not always have the ability to detect all the events reported by a specific dive computer.

Events are indicated by symbols on the dive profile. Notifications are shown as a white, round symbol with a letter i; warnings are indicated by a yellow triangle and alarms by a red triangle. By moving the cursor over a symbol, the explanation is given in the bottom-most line of the Information Box (see image below, where the cursor is positioned over the alarm that was reported).

Some dive computers report bookmarks that the diver has set during the dive. These are indicated as a small red flag on the profile and are discussed more fully in the section on inserting bookmarks.

The dive profile can include graphs of the partial pressures of O₂, N₂, and He during the dive (see figure above) as well as a calculated and dive computer reported deco ceilings (only visible for deep, long, or repetitive dives). Partial pressures of oxygen are indicated in green, nitrogen in black, and helium in dark red. These partial pressure graphs are shown below the profile data.

The air consumption graph displays the tank pressure and its change during the dive. The air consumption takes depth into account so that even when manually entering the start and end pressures the graph, is not a straight line. Like the depth graph, the slope of the tank pressure provides information about the momentary SAC rate (Surface Air Consumption) when using an air integrated dive computer. Here the color coding is not relative to some absolute values but relative to the mean normalized air consumption during the dive. So areas in red or orange indicate times of increased normalized air consumption while dark green reflects times when the diver was using less gas than average.

When in planner mode, the SAC is set to be constant during the bottom part of the dive as well during decompression. Therefore, when planning a dive, the color is a representation of the breathing gas density.

It is possible to zoom into the profile graph. This is done either by using the scroll wheel / scroll gesture of the mouse or trackpad. By default Subsurface always shows a profile area large enough for at least 30 minutes and 30m (100ft) – this way short or shallow dives are easily recognizable; something free divers won’t care about.

The profile can also include the dive computer reported ceiling (more precisely, the deepest deco stop that the dive computer calculated for each particular moment in time) as a red overlay on the dive profile. Ascent ceilings occur when a direct ascent to the surface increases the risk of a diver suffering from decompression sickness (DCS) and it is necessary to either ascend slower or to perform decompression stop(s) before ascending to the surface. Not all dive computers record this information and make it available for download; for example none of the Suunto dive computers make these data available to divelog software. Subsurface also calculates ceilings independently, shown as a green overlay on the dive profile. Because of the differences in algorithms used and amount of data available (and other factors taken into consideration at the time of the calculation) it’s unlikely that ceilings from dive computers and from Subsurface are the same, even if the same algorithm and gradient factors (see below) are used. It’s also quite common that Subsurface calculates a ceiling for non-decompression dives when the dive computer stayed in no-deco mode during the whole dive (represented by the dark green section in the profile at the beginning of this section). This is because Subsurface’s calculations describe the deco obligation at each moment during a dive, while dive computers usually take the upcoming ascent into account. During the ascent some excess nitrogen (and possibly helium) are already breathed off so even though the diver technically encountered a ceiling at depth, the dive still does not require a specific deco stop. This feature lets dive computers offer longer non-stop bottom times.

Strictly speaking, the green calculated ceiling is a direct representation of the inert gas loadings of the simulated tissues only and is independent of any assumed ascent velocities. It indicates the deco model’s minimal allowed depth at this instant of time given the inert gas loadings and is not a statement about a possible ascent schedule in the remaining dive. To obtain the latter, use the "Edit dive in planner" option from the Log menu.

The context menu for the Dive Profile is accessed by right-clicking while the mouse cursor is over the Dive Profile panel. The menu allows creating Bookmarks, Gas Change Event markers, or manual CCR set-point changes other than the ones that might have been imported from a Dive Computer. Markers are placed against the depth profile line, with the time of the event determined by the mouse cursor when the right mouse button was clicked to bring up the menu. Gas Change events involve a selection of which gas is being switched TO. The list of choices is based on the available gases defined in the Equipment Tab. Setpoint change events open a dialog letting you choose the next setpoint value. As in the planner, a setpoint value of zero shows the diver is breathing from an open circuit system while any non-zero value shows the use of a closed circuit rebreather (CCR). By right-clicking while over an existing marker a menu appears, adding options to allow deletion of the marker, or to allow all markers of that type to be hidden. Hidden events can be restored to view by selecting Unhide all events from the context menu.

However, filtering can be performed in a much more precise way by adding constraints to the filter panel. Clicking the Load Constraints button (located near the top left-hand of the filter panel) brings up a list of the terms that could be selected for filtering the Dive List.

For instance, selecting the constraint "Location" from this list adds a line to the filter panel for specifying the location constraint. For instance, typing "Sodwana" into the Locality text box brings up all the dives for which the dive location was given as Sodwana. There are two combo-boxes associated with the Location constraint. Selecting "is not" from the first combobox allows showing all the dives that were NOT performed at Sodwana. The second combobox operates in a similar way to that of the Full-text filter as described above (first part of word, complete word, contains-word). Constraints can be refined in one of two ways:

We may wish to refine our selection of dives to show in the Dive List. Let’s say we wish to show dives for which the water temperature was 18 °C or higher. Select "Water Temp." from the list of constraints. A line containing this new constraint is added to the filter panel. Select "at least" from the combobox on this line and type "18" in the appropriate text box. Below is an image with constraints defined to filter dives at Sodwana with water temperatures at 18 °C or higher.

In order to refine our filter we may wish to show only dives on a Tuesday. Select "week day" from the list of constraints. A line containing this new constraint is added to the filter panel with a dropdown list of days that are selectable. Select "Tuesday" from the list. The image below shows a filter that selects dives at Sodwana on Tuesdays with the water temperature at or above 18 °C.

As a last step in refining our filter we may wish to add another constraint specifying visibility of at least three stars. Select "visibility" from the list of constraints. A new line is added to the filter panel, allowing us to select the number of stars we require. In this case click on the third star and ensure that the combobox shows "at least". We have now filtered for all dives at Sodwana on a Tuesday with water temperature at or above 18 °C and with a 3-star or better visibility.

Clearly it is possible to construct highly refined filters. The examples above show only a tiny fraction of the possibilities in creating filters.

Deleting a constraint: A constraint can be removed from the filter by clicking the appropriate dustbin icon on the left of the filter panel.

We need to define a new term: "Filter sets". A "Filter set" is a combination of constraints that have been defined to form a filter, as in our example above. Specifying a filter set (as above) can take some time and experimentation, and we may wish to save this set for later use. Save the set by clicking the button "Save set". A text box opens to provide a name for this set. Provide a set name, click the OK button and the set is now permanently saved as part of the overall dive log.

If you wish to access the filter set on a later date, click the button "Load set". This provides a list of sets that have been saved. Select the set you wish to use. It is loaded into the filter panel, showing the name of the set in the top line of the panel immediately following "Current set:"

Filter sets can be deleted by selecting the "Filter sets" tab in the Filter Panel and by clicking on the dustbin icon on the left of the appropriate filter set name.

The filter action can only be stopped by using the Reset button (yellow up-arrow) or by manually deleting any full-text specification as well as all the constraints with associated dustbin icons. Closing the Filter Panel does not terminate filtering: the filtered dive list remains unchanged. This is obvious from the top bar of the Subsurface window indicating that only some of all the dives are shown. Closing the Filter Panel activates the Map Panel, allowing viewing the map locations of the filtered dive list. For instance one might wish to filter on Bob Smith as a buddy. Closing the Filter Panel allows viewing the map locations where Bob Smith was a buddy. To re-open the Filter Panel in this case, select Log → Filter divelist from the Main Menu. To switch off filtering and exit the Filter Panel, click on Reset and then on Close.

By default, when the Statistics panel is opened, a histogram is shown of the number of dives performed each year. This is an example of counts data. To request a graph representing counts, three comboboxes need to be set:

a) The top combobox of the Base variable needs to be specified. Which variable should be along the horizontal axis? Examples are Year, Buddy, Rating, Max. depth.

b) The binning combobox for the Base variable needs to be specified. This represents the increment for each bar along the horizontal axis. For instance, when counts of number of dives are extracted for years, this could be in increments of a year, a quarter (3 month period) or a month. For some variables, e.g. Buddy or Rating, a binning value is not relevant and cannot be selected. However, for others, e.g. Year or Max. depth, selecting the appropriate binning is important.

c) For simple counts data, the top combobox of the Data variable needs to be set to "none". This is because a data variable is not involved in this type of graph. Divers used to spreadsheets may prefer a pie chart for these data, achieved by selecting "Categorical/piechart" from the Chart combobox. It is possible to simultaneously provide counts for two variables. In this case one could specify a Data variable which results in the counts being subdivided according to the data variable. This option does not have a piechart equivalent. Detailed information for each bar can be obtained by hovering the mouse over the the appropriate bar.

For simple histograms, the default height of each bar is determined by the mean value for the observations included in each bar. However, this can be manipulated using the Operation combobox to show the mean, maximum, minimum, median and sum applicable to each bar. Image A below shows quarterly count data of dives while image B shows quarterly count data, subdivided by dive mode (some dives open circuit, other dives rebreather). The mouse is positioned over a specific bar to provide detailed information. The legend can be dragged around so that it does not obscure part of the graph. Alternatively, the legend can be removed by deselecting the appropriate checkbox at the bottom left of the setup panel.

Sometimes you might wish to investigate the relationship between two dive variables. Has my SAC rate decreased over the years? Is the water temperature colder at greater dive depth? One of the ways of investigating these questions is to draw a scattergraph where the values of one variable is plotted against the other variable (see image below).

For the dataset in the above image, the SAC rate appears to have decreased over time. If the "linear regression" checkbox is marked, a red line is shown that summarizes the best estimate of the relationship between SAC rate and year. In this graph it appears that SAC rate has decreased from around 21 l/min to around 14 l/min between 2013 and 2021. The pink area around the red line indicates the uncertainty of the precise orientation of the line. The line is expected to lie somewhere within the pink area with a certainty of 95%. The intensity of the pink color also indicates the relative reliability of these estimates. The procedure for obtaining a scattergraph is:

a) Specify the Base variable: Which variable should be along the horizontal axis? Examples are Date, Temperature, Max. depth, SAC rate.

b) Set the binning value for the Base variable to "none".

c) Specify the Data variable: Which variable should be along the vertical axis?

Within the scattergraph, hover over a specific point to see more information for that point.

You might also wish to compare different categories of dives. Is the (5-star) Rating of a dive related to water temperature? Is my SAC rate related to diving with different dive suits? Since dive suit and Rating are categories, a scattergraph is not appropriate. The default is a categorical dot graph, which, in the case of image A below, shows the precise water temperatures for each Rating. The red lines indicate the top quartile, the mean and the lower quartile of temperature for each rating. The column with no star indicates dives for which a Rating has not been selected. It appears that dives with a 5-star rating have higher temperatures that the other ratings. To obtain a categorical graph:

a) Select a variable with categories (along the horizontal axis) as a Base variable.

b) Select the data variable and set binning to "none".

c) By default the Chart combobox shows "Categorical/data points". If this is not the case, select this value.

Alternatively you could create a Box-whisker graph for the same data. In the Chart combobox, select "Categorical/box-whisker". This creates a graph indicating the maximum, top quartile (Q3), median, bottom quartile (Q1) and minimum for each category or class. Image B above shows a box-whisker graph for the same data as image A above. You can see that the values for a Rating of 5 stars tend to be higher than for other ratings. Hover over a box to see more complete information for that box.

As explained in the section above on counts data, bar-charts showing a breakdown of each category for a number of subcategories is easy (images below).

a) Select a variable with categories (along the horizontal axis) as a Base variable (e.g. dive mode or suite type).

b) Select another category of data as a Data variable (e.g. gas type or cylinder type).

The images below show two alternative bar-chart representations. If, in the Chart combobox, one selects "Barchart/stacked vertical", a graph similar to image A below is generated. This summarized a log of technical dives where, for each cylinder gas type, the bar is subdivided into a count for open-circuit dives and for rebreather dives. On the other hand, if "Barchart/grouped vertical" is selected in the Chart combobox, a graph similar to image B, below, is produced. Here the subdivision within each gas type is shown as adjacent bars.

Bar-charts can be rotated by 90 degrees by selecting the appropriate chart type in the Chart combobox. For instance, here is the horizontal bar-chart produced when selecting "Barchart/stacked horizontal" in the Chart combobox and using the same dataset as in the graph above. This is useful if the labels for different bars are long, preventing them being displayed with vertical bar charts.

Let’s say you are viewing a bar graph showing mean maximum dive depth for different years. However two of the years have dive depth values that appear atypical and you wish to inspect the dives only for those two years. The obvious approach is to use the Filter tool to select only data for the two years of interest and then view those data using the Statistics panel. However, Subsurface provides a rapid mechanism of selecting the appropriate subset of data using your mouse. In the above example of a bar graph, select the bars for the two years of interest by clicking on them and activate the "Restrict to selection" button towards the bottom left of the Statistics panel. This displays only the data for the two bars that have been selected. This restricted subset can now be analyzed using all the options in the Statistics panel. Below is a scattergraph for a number of dives, showing the water temperature for different dive depths.

Let’s say you wish to analyze only dives at tropical dive sites, defined by temperatures above 22°C and depths less than 60m. Select the appropriate dives by dragging your mouse across the scattergraph (see image above) and restrict the data by activating the "Restrict to selection" button. Now only the selected subset of points is shown on the graph. You can now select Base and Data variables to further analyze the restricted data. The graph below shows the SAC rates as a function of dive depth for the restricted dataset created above. The graph shows that SAC rate was more or less constant (around 15 l/min) for all dive depths at tropical dive sites.

The ability to rapidly create subsets of data for display (using the restriction tool) creates a powerful mechanism to do rapid but detailed analysis of a dive log.

After creating a data subset, The text in the restriction tool indicates the number of dives in the subset that has been selected. Note, in the figure above, that a previously greyed-out button, "Reset restriction", has been made active after restricting the data for graphing. The original dataset can be restored by clicking the "Reset restriction" button. The text in the restriction tool now shows "Analyzing all dives".

The default information in the Dive List includes, for each dive, Dive_number, Date, Rating, Dive_depth, Dive_duration and Dive_location. This information can be controlled and changed by right-clicking on the header bar of the Dive List, bringing up a list of columns that can be shown in the dive list (see above). Check an items to be included in the Dive List. The list is immediately updated. Preferences for information shown in the Dive List are saved and used when Subsurface is re-opened.

By selecting the Media checkbox in the dropdown list, an icon is shown indicating whether any media are associated with a particular dive. There are three icons:

Normally, in the dive list, minimal information is included in the trip title. More information about a trip can be added by selecting its trip title bar from the Dive List. This shows a Trip Notes tab in the Notes panel. Here you can add or edit information about the date/time, the trip location and any other general comments about the trip as a whole (e.g. the dive company that was used, the general weather and surface conditions during the trip, etc.). After entering this information, select Save from the buttons at the top right of the Trip Notes tab. The trip title in the Dive List panel should now reflect the edited information.

Once the dives have been grouped into trips, you can expand one or more trips by clicking the expansion button [+/-] on the left of each trip title. This expands the selected trip, revealing individual dives during the trip.

After selecting a trip title, the context menu allows the merging of trips by either merging the selected trip with the trip below or with the trip above. (Merge trip with trip below; Merge trip with trip above)

If a trip includes, for example, ten dives, you can split this trip into two trips (trip 1: top four dives; trip 2: bottom six dives) by selecting and right-clicking the top four dives. The resulting context menu lets the user create a new trip by choosing the option Create new trip above. The top four dives are then grouped into a separate trip. The figures below show the selection and context menu on the left (A) and the completed action on the right (B):

Dives can be permanently deleted from the dive log by selecting and right-clicking them to bring up the context menu, then selecting Delete dive(s). Typically this would apply to a case where a user wishes to delete workshop calibration dives of the dive computer or dives of extremely short duration.

You can unlink dives from the trip to which they belong. To do this, select and right-click the relevant dives to bring up the context menu. Then select the option Remove dive(s) from trip. The dive(s) now appear immediately above or below the trip to which they belonged, depending on the date and time of the unlinked dive.

Selected dives can be moved from the trip to which they belong and placed within a separate trip. To do this, select and right-click the dive(s) to bring up the context menu, and then select Create new trip above.

Sometimes it’s necessary to adjust the start time of a dive. This may apply to situations where dives are done in different time zones or when the dive computer has a wrong time. To do this, select and right-click the dive(s) to be adjusted. This brings up the context menu on which the Shift times option should be selected. You must then specify the time (in hours and minutes) by which the dives should be adjusted and click on the option of whether the time adjustment should be earlier or later.

Sometimes a dive is briefly interrupted, for example, if a diver returns to the surface for a few minutes, resulting in two or more dives being recorded by the dive computer and appearing as different dives in the Dive List panel. Merge these dives onto a single dive by selecting the appropriate dives, right-clicking them to bring up the context menu and then selecting Merge selected dives. It may be necessary to edit the dive information in the Notes panel to reflect events or conditions that apply to the merged dive. The figure below shows the depth profile of two dives that were merged:

On some occasions, a diver reaches the surface and immediately dives again. However, it may happen that the dive computer does not register a new dive, but continues the previous dive due to the brief surface interval. In this case it is possible to split a dive so that the two dives are shown as independent dives on the Dive List. If this operation is performed, Subsurface scans the selected dive(s) and splits the dive at points during the dive where the depth is less than a meter.

This topic is discussed in the section: Adding photographs or videos to dives.

This topic is discussed in the section: Adding photographs or videos to dives.

Important actions on dives or trips, described above, can be undone or redone. This includes: delete dives, merge dives, split selected dives, renumber dives and shift dive times. To do this after performing any of these actions, from the Main Menu select Edit. This brings up the possibility to Undo or Redo an action.

Recreational mode is intended for what most divers would call "recreational", "sports"or "nontechnical" dives, remaining within no-deco limits (NDL). It computes the maximum time a diver can stay at the current depth without needing mandatory decompression stops and without using more than the existing gas (minus a reserve). The planner automatically takes into account the nitrogen load incurred in previous dives. But conventional dive tables are also used in a way that can take into account previous dives. Why use a dive planner for recreational dives? The subsurface dive planner provides two significant advantages over the use of recreational dive tables for dive planning.

Firstly, using recreational dive tables, the maximum depth of each previous dive is taken into account. But few dives are done at a constant depth corresponding to the maximum depth (i.e. a "square" dive profile). This means dive tables overestimate the nitrogen load incurred during previous dives. The Subsurface dive planner calculates nitrogen load according to the real dive profiles of all uploaded previous dives, in a similar way as dive computers calculate nitrogen load during a dive. This means that the diver gets credit, in terms of nitrogen load, for not remaining at maximum depth during previous dives, so a longer subsequent dive can be planned. For the planner to work it’s therefore crucial to log previous dives in Subsurface before doing dive planning.

Secondly, recreational dive tables are not designed to build additional safety features into a dive. NDL times derived from dive tables often take divers close to the limit where decompression sickness (DCS) can arise. The Subsurface dive planner allows a diver to build more safety features into a dive plan, preventing recreational divers from getting close to the limits of getting a DCS hit. This is performed by specifying appropriate gradient factors for a dive plan, as explained below.

To plan a dive, the appropriate settings need to be defined.

Below is an image of a dive plan for a recreational dive at 30 meters with gradient factors of 100. Because the no-deco limit (NDL) is 22 minutes, there remains a significant amount of air in the cylinder at the end of the dive.

The dive profile in the planner shows the maximum dive time within no-deco limits using the Bühlmann ZH-L16 algorithm and the gas and depth settings specified as described above. The Subsurface planner allows rapid assessment of dive duration as a function of dive depth, given the nitrogen load incurred during previous dives. The dive plan includes estimates of the amount of air/gas used, depending on the cylinder settings specified under Available gases. If the start cylinder pressure is left blank, the dive duration shown is the true no-deco limit (NDL) without taking into account gas used during the dive. If the surface above the dive profile is RED it means that recreational dive limits are exceeded and either the dive duration or the dive depth needs to be reduced.

Below is the same dive plan as above, but with a safety stop and reduced gradient factors for a larger safety margin.

Non-recreational dive planning involves exceeding the no-deco limits and/or using multiple breathing gases. These dives are planned in three stages:

a) Nitrogen management: This is done by specifying the rates for descent and ascent, as well as the deco model (GFLow, GFHigh or Conservatism level) under the headings Rates and Planning to the bottom left of the planning screen. Two deco models are supported the Bühlmann model and the VPM-B model. Select one of the two models. When selecting the Bühlmann model, the gradient factors (GFHigh and GFLow need to be specified. Initially, the GFHigh and GFLow values in the Tech setup preferences panel of Subsurface is used. If these are changed within the planner (see Gas Options within the planner), the new values are used without changing the original values in the Preferences. Gradient Factor settings strongly affect the calculated ceilings and their depths. A very low GFLow value brings on decompression stops early during the dive.

If the VPM-B model is selected, the Conservatism_level needs to be specified on a scale of 0 (least conservative) to 4 (most conservative). This model tends to give deco stops at deeper levels than the Bühlmann model and often results in slightly shorter dive durations than the Bühlmann model, albeit at the cost of higher tissue compartment pressures in the slow tissues. When selecting one of these models, keep in mind they are NOT exact physiological models but only mathematical models that appear to work in practice.

Please note as well that there is an intrinsic assumption of the VPM-B model that off-gassing only happens during the ascent phase of the dive (which is the part controlled by the planner). Thus it is possible to get misleading results if you manually enter waypoints well in the decompression phase of your dive. This is particularly relevant when editing a dive read from disk in the planner since that will have waypoints up to the surface. Thus for those dives, first delete all waypoints during the ascent phase. This is most easily done by holding the Ctrl- or Command-key while clicking on the trash can icon next to the first ascent waypoint in the table on the left hand side.

For more information external to this manual see:

The ascent rate is critical for nitrogen off-gassing at the end of the dive and is specified for several depth ranges, using the mean depth as a yardstick. The mean depth of the dive plan is shown by a light grey line on the dive profile. Ascent rates at deeper levels are often in the range of 8-12 m/min, while ascent rates near the surface are often in the range of 4-9 m/min. The descent rate is also specified. If the option Drop to first depth is activated, the descent phase of the planned dive will be at the maximal descent rate specified in the Rates section of the dive setup.

b) Oxygen management: In the Gas Options part of the dive specification, the maximum partial pressure for oxygen needs to be specified for the bottom part of the dive (bottom po2) as well as for the decompression part of the dive (deco po2). Commonly used values are 1.4 bar for the bottom part of the dive and 1.6 bar for any decompression stages. Normally, a partial pressure of 1.6 bar is not exceeded. The depth at which switching to a gas takes place can be edited in the Available Gases dialog. Normally, the planner decides on switching to a new gas when, during ascent, the partial pressure of the new gas has decreased to 1.6 bar.

c) Gas management: With open-circuit dives this is a primary consideration. Divers need to keep within the limits of the amount of gas within the dive cylinder(s), allowing for an appropriate margin for a safe return to the surface, possibly sharing with a buddy. Under the Gas Options heading, specify the best (but conservative) estimate of your surface-equivalent air consumption (SAC, also termed RMV) in liters/min (for the time being, only SI units are supported). Specify the SAC during the bottom part of the dive (bottom SAC) as well as during the decompression or safety stops of the dive (deco SAC). Values of 15-30 l/min are common. For good gas management, a guess is not sufficient and you needs to monitor gas consumption on a regular basis, dependent on different dive conditions and/or equipment. The planner calculates the total volume of gas used during the dive and issues a warning if you exceeds the total amount of gas available. Good practice demands that divers not dive to the limit of the gas supply but that an appropriate reserve is kept for unforeseen circumstances. For technical diving, this reserve can be up to 66% of the total available gas. In addition to calculating the total gas consumption for every cylinder the planner provides one way of calculating the recommended volume of bottom gas which is needed for safe ascent to the first deco gas change depth or the surface. This procedure is called the "minimum gas" or "rock bottom" consideration and it is used by various (but not all) technical diving organizations. See the text below for a detailed explanation.

Now you can start the detailed time-depth planning of the dive. Subsurface offers an unique graphical interface for doing planning. The mechanics are similar to hand-entering a dive profile in the dive log part of Subsurface. Upon activating the planner, a default dive of depth 15 m for 20 min is offered in the blue design surface in the top right hand part of the planner window. The white dots (waypoints) on the profile can be dragged with a mouse. Create more waypoints by double-clicking on the profile line and ensuring the profile reflects the intended dive. Drag the waypoints to represent the depth and duration of the dive. It is NOT necessary to specify the ascent part of the dive since the planner calculates this, based on the existing settings. If any of the management limits (for nitrogen, oxygen or gas) are exceeded, the surface above the dive profile changes from BLUE to RED.

Each waypoint on the dive profile creates a Dive Planner Point in the table on the left of the dive planner panel. Ensure the Used Gas value in each row of that table corresponds to one of the gas mixtures specified in the Available Gases table. Add new waypoints until the main features of the dive have been completed, e.g. the bottom time segment and deep stops (if these are implemented). In most cases Subsurface computes additional way points in order to fulfill decompression requirements for that dive. A waypoint can also be moved by selecting it and by using the arrow keys. The waypoints listed in the Dive Planner Points dialog can be edited by hand in order to get a precise presentation of the dive plan. In fact, it is sometimes more easy to create the whole dive profile by editing the Dive Planner Points dialog.

Show any changes in gas cylinder used by indicating gas changes as explained in the section hand-creating a dive profile. These changes should reflect the cylinders and gas compositions defined in the table with Available Gases. If two or more gases are used, automatic gas switches will be planned during the ascent to the surface.

Cylinders used for the plan need to be entered in the table of Available gases. In the column Type select the appropriate cylinder size by using the dropdown list that appears when double-clicking a cell in this column. By default, a large number of sizes are listed, and a new cylinder size can be created by typing this into the text box. The cylinder size, start pressure and default switch depths are initialized automatically. Specify the gas composition (e.g. helium and oxygen content). A non-zero value in the "CC setpoint" column of the table of dive planner points indicates a valid setpoint for oxygen partial pressure and that the segment is dived using a closed circuit rebreather (CCR). If the last manually entered segment is a CCR segment, the decompression phase is computed assuming the diver uses a CCR with the specified set-point. If the last segment (however short) is on open circuit (OC, indicated by a zero set-point) the decompression is computed in OC mode and the planner only considers gas changes in OC mode.

Enter dive profile segments in the Dive planner points table by providing a time duration for a segment as well as its final depth. If more than one cylinder is used during the dive, ensure that the appropriate cylinder is selected for each segment of the dive plan by double-clicking the cell and selecting the appropriate cylinder from the dropdown list in the Used gas column. If required, insert a row in the Dive planner points table by adding a new line and then setting the Run time value appropriately. In image A below, a segment (using an EAN50 cylinder) has been added and you wish to use this gas during the very start of the dive (the other gas is not breathable at the surface). Upon pressing Enter on the keyboard, that segment is moved to the top of that table and the plan is adjusted automatically to take into account this new segment of the dive plan (image B below).

Below is an example of a dive plan to 55m using Tx20/30 and the Bühlmann algorithm, followed by an ascent using EAN50 and using the settings as described above.

Once the above steps have been completed, save by clicking the Save button towards the top middle of the planner. The saved dive plan will appear in the Dive List panel of Subsurface.

The dive plan details

On the bottom right panel of the dive planner, under Dive Plan Details, the details of the dive plan are provided. These may be modified by checking any of the options under the Notes section of the dive planner, immediately to the left of the Dive Plan Details. If a Verbatim dive plan is requested, a detailed sentence-level explanation of the dive plan is given. If any of the management specifications have been exceeded during the planning, a warning message is printed underneath the dive plan information.

If the option Display segment duration is checked, then the duration of each depth level is indicated in the Dive Plan Details. This duration INCLUDES the transition time to get to that level. However, if the Display transition in deco option is checked, the transitions are shown separately from the segment durations at a particular level.

Dive plan variations: The planner has a check box Display plan variations. By checking this box, the planner provides information about a dive that is a little deeper or slightly longer than the planned dive. This is found near the top of the Dive plan details where the dive duration is indicated. The information is intended to be used if it is necessary to modify the ascent "on the fly" in the case of unexpected deviations from the dive plan during the dive. For example, if it says "Runtime: 123min, Stop times + 2:49 /m + 1:30 /min" this means: if you dive deeper than planned, you should add almost 3 minutes per meter you go deeper to your decompression (and you can subtract 3 minutes per meter that you stay shallower). If you overstay your bottom time, you need to add one and a half minutes to the stops for each minutes you overstay and similarly, you can shorten your deco time by one and a half minute for each minute you stay shorter. These variations of depth and time are based on the last manually entered segment of the dive (not necessarily the deepest). The additional minutes should be distributed over the different stops in a way proportional to the stop length, i.e. add more of the additional minutes to the longer, shallower stops. The given times refer to the duration of the decompression phase and do not include the extended bottom time! This way of altering dive plans becomes inaccurate for large deviations from the original plan. So it should not be trusted for more than a few minutes or meters of deviations from the planned bottom time. Checking this option creates a lot of additional computation, to such a degree that the planner is slower than otherwise.

Minimum gas requirements: The planner also estimates the minimum gas pressure required for safe ascent after an event that causes the dive to be aborted. The calculation assumes that in worst case an out of gas (OoG) situation occurs at the end of the planned bottom time at maximum depth, requiring additional time at maximum depth to solve the problem and forcing the buddy pair the share the gas of one diver. In addition the combined SAC of both divers is increased by an estimated factor compared to the SAC of a single diver under normal conditions. The result of the minimum gas calculation for the bottom gas is printed to the planner output. There are two selector boxes on the left of the Dive plan details:

Using the above information, the planner then estimates what the minimum bottom gas cylinder pressure needs to be for a safe ascent. This information is given near the bottom of the Dive plan details, following the calculation of bottom gas used during the dive if it exactly follows the plan. the minimum gas is typically given as:

This indicates:

No automatic checks are performed based on this result. The feature only gives valid results for simple, rectangular shaped single level dive profiles. For multi level dives one would need to check every leg of the profile independently.

Isobaric counterdiffusion information: For gas switches during the ascent in hypoxic open-circuit trimix dives information about isobaric counterdiffusion (icd) is given near the bottom of the Dive plan details, based on the rule-of-fifths (i.e. during a gas change, the increase in nitrogen partial pressure should not exceed one fifth of the corresponding decrease in partial pressure of helium). For each gas change, two lines are printed, indicating the changes in gas fractions (%) and the equivalent changes in partial pressures. If the rule-of-fifths is not met, the relevant information is highlighted in red and a warning message appears at the bottom of that table. The gas change events on the dive profile also provide information on icd, visible at the bottom of the Information box when the mouse hovers on the respective gas change icon. This information is only shown for gas changes relevant with respect to icd. If the rule-of-fifths is not met, a red warning exclamation mark is shown over the gas change icon. When relevant, the Information box contains information such as: ICD ΔHe:-13% ΔN₂+3%>2.6%. This means: for this gas change, the helium decreased with 13% while the nitrogen increased with 3% which is more than the 2.6% maximum increase in nitrogen suggested by the rule-of-fifths.

In the case of a pSCR dive plan for open water, the worst-case scenario is probably bailout at the end of the deepest part of the dive and this could be achieved using the Bailout checkbox of the planner. Alternatively create a 1-minute segment at the end of the deepest part of the dive plan. This last segment (represented by the bottom row of the Dive planner points table) is then manipulated using the Dive mode and Used gas columns, as in the cave example, above. See the example of bailout for a CCR dive, below, that uses this approach.

The volumes of gases required for bailout can be found at the bottom of the Dive plan details panel.

Bluetooth is most likely already enabled. For pairing with the dive computer choose Control Panel → Bluetooth Devices → Add Wireless Device. This should bring up a dialog showing your dive computer (which should be in Bluetooth mode) and allowing pairing. Right click on it and choose Properties→ COM Ports to identify the port used for your dive computer. If there are several ports listed, use the one saying "Outgoing" instead of "Incoming".

For downloading to Subsurface, the Subsurface drop-down list should contain this COM port already. If not, enter it manually.

Note: If there are issues afterwards when downloading from the dive computer using other software, remove the existing pairing with the dive computer.

Click on the Bluetooth symbol in the menu bar and select Set up Bluetooth Device…. The dive computer should then show up in the list of devices. Select it and go through the pairing process. This step should only be needed once for initial setup.

Once the pairing is complete, the correct device is shown in the Device or Mount Point drop-down in the Subsurface Import dialog.

Be sure Bluetooth is enabled on the Subsurface computer. On most common distributions this should be true out of the box and pairing should be straightforward. For instance, Gnome3 shows a Bluetooth icon on the right of the toolbar at the top of the screen. Users have reported difficulties with some Bluetooth controllers. If you have an onboard controller, try that first. It is simplest if you remove any USB Bluetooth dongles. If you have a USB dongle that came with your dive computer, try that before any others.

Setting up a connection to download dives from your Bluetooth-enabled device, such as the Shearwater Petrel, is not yet an automated process and will generally require the command prompt. It is essentially a three step process.

Ensure the dive computer is in upload mode. On the Shearwater Petrel, Petrel 2 and Nerd cycle through the menu, select Dive Log, then Upload Log. The display will read Initializing, then Wait PC 3:00 and will countdown. Once the connection is established, the display reads Wait CMD … and the countdown continues. When downloading the dive from Subsurface, the display reads Sending then Sent Dive.

To establish the connection, establish root access through sudo or su. The correct permission is required to download the dives in the computer. On most Linux systems this means becoming a member of the dialout group (This is identical as for many dive computers using a Linux USB port, described in the previous section). On the command terminal, enter:

sudo usermod -a -G dialout username

Then log out and log in for the change to take effect.

Open the following web address: https://cloud.subsurface-divelog.org/passwordreset

This will require that you enter the same email address that you used during cloud registration.