Subsurface is an open source divelog program that runs on Windows, Mac and Linux.
Subsurface is able to track single- and multi-tank dives using air, Nitrox or TriMix. It allows tracking dive locations including GPS coordinates (which can also conveniently be entered using a map interface), logging of equipment used and other people on the dive, and enables the user to rate dives and provide additional dive notes. Users can provide tags for each dive and filter their dive list based on a variety of criteria including tags, locations and people you were diving with. Subsurface calculates a wide variety of statistics of the user’s diving and calculates and tracks information like the user’s SAC rate, partial pressures of O2, N2 and He, calculated deco information, and many more.
One of the major strength of Subsurface is its support of a wide range of dive computers (see the list of supported dive computers). Subsurface can also import existing dive logs from several sources including MacDive, Suunto DM3, DM4 & DM5, JDiveLog and divelogs.de. Another strength is its ability to visualize the depth profile (and, if available, the tank pressure curve) in very innovative ways that give the user additional information on relative velocity (and momentary air consumption) during the dive.
Subsurface allows the user to print out a detailed log book including dive profiles and other relevant information.
The program is localized in about 20 languages and well supported by an active developer community.
A bit of background:
In fall of 2011, when a forced lull in kernel development gave him an opportunity to start on a new endeavor, Linus Torvalds decided to tackle his frustration with the lack of decent divelog software on Linux.
Subsurface is the result of the work of him and a team of developers since then. It now supports Linux, Windows and MacOS and allows data import from a large number of dive computers and several existing divelog programs. It provides advanced visualization of the key information provided by a modern dive computer and allows the user to track a wide variety of data about their diving. In fall of 2012 Dirk Hohndel has taken over as Subsurface maintainer.