Subsurface is described as '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' and is an app. There are six alternatives to Subsurface for a variety of platforms, including iPhone, iPad, Mac, Windows and Android apps. The best Subsurface alternative is Diving Log. It's not free, so if you're looking for a free alternative, you could try DiverLog or Plancto. Other great apps like Subsurface are Dive Log, Deep Tools and Dive.site.