The computer you're diving SP2 Sporasub is a watch that can be used for the apnea as well as for training sessions out of the water. It is sold with its PC interface cable. The main functions of the computer SP2 are: Scuba Diving, clock, count down reboiurs, mlémoire, and settings. This computer is very intuitive, and making it easy to use. The Dive Master and the SP2 software (download) are easy to use and changing all the time. The two can be updated via an internet connexion via a dedicated icon on the site of Sporasub. There is an optional heart rate monitor, but if you would like this, be sure to cheque out the being produced up x1 Omer Pelizzari which will have all the features you want.