It does not calculate depth according to the manufacturer’s information. The bezel is marked in accordance with the recommended rate of ascent rather than being a dive timer. Check their web site.
mdemeyerAfter watching the tutorial, it appears that it is simply a bezel that you rotate to your dive DEPTH as coordinated with the minute hand at the time of ASCENT using the Navy dive ascent rate; as the minute hand proceeds, it indicates ONLY your ascent and safety stop. This bezel does not rotate on its own or indicate anything other than elapsed time... just as a standard bezel would.
While I have bought this watch, I would not count on it as anything other than a backup device to my computer and depth gauge. It is a cool timepiece and novelty. Not a valid diving timer of any type as it doesn't comport with good dive practice, other than the safety stop if you are good enough to set your max depth with the bezel.
I could be wrong, but this seems to be how this device works. I will report when it arrives!
DakotabHaven't read much about the dial but agree with comment as purely a backup device. I love to look at my diver's while diving but the computer does the serious work. Always good to have a backup though. Plus I can justify buying more divers!