This is the Sporasub SP2 Free Diving Spearfishing Computer Dive Watch Features: Freedive mode Chrono mode Dive Master software SP2 it&';s a perfect combination of functionality and style, both for freediving and dry" training. Its main features are: DIVE, CHRONO, TIMER, HISTORY, SET-UP. The Dive Master software (available at Omersub website) allows dive data downloading of: dive time, maximum depth, water temperature, total calories, max/min heart rate (only using Cardio Chest Strap). The Cardio Chest Strap (optional - not included) can be used both in Dive and Chrono mode. It features 5,3 KHz allowing underwater data transmission. Software and SP2 Firmware are very easy to use and their updating is available at Dive Master when released. "