Subsurface is described as 'can plan and track single- and multi-tank dives using air, Nitrox or TriMix'. There are five alternatives to Subsurface for a variety of platforms, including Mac, Windows, iPhone, iPad and SaaS. The best alternative is Plancto, which is free. Other great apps like Subsurface are Diving Log (Paid), DiverLog (Freemium), Dive Log (Freemium) and Dive.site (Free).
Plancto is a personal scuba logbook that allows to you quickly see all your dive in the map, collects stats about your dive history, allows you to collect to your buddies and tracks your air consumption overtime. All history can be downloaded and printed or exported.
Diving Log is the perfect scuba logbook solution to manage your dives. You can import your dive log data from almost every dive computer, either by importing from the manufacturer software or by direct download from the dive co
Dive Log (and Dive Log Manager / Dive Log DT for Mac desktop) provides full featured dive logging, display of logged information and statistics, integration with iOS features, and logbook exchange with your desktop computer.
Dive.site is an interactive map for divers which you can use to search and add dive sites, keep track of your own dives and share impressions about your diving experience with other members. To begin all you need is an account, which is free.