Subsurface can plan and track single and multi-tank dives using air, Nitrox or
TriMix. It allows tracking of dive locations including GPS coordinates (which
can also conveniently be entered using a map interface), logging of equipment
used and names of other divers, and lets users rate dives and provide
additional notes.

You can tag dives and filter a dive list based on criteria including tags,
locations and people with whom you were diving. You can group the dive list
into trips, and edit multiple dives at the same time, making it easy to support
a large number of dives.

Subsurface also calculates a wide variety of statistics of the user's diving
and tracks information like the SAC rate, partial pressures of O2, N2 and He,
calculated deco information, and many more.