well, my criteria would be:
- accurate and reliabel
- waterresistant (200m real)
- high readibility (with good luminescense)
- no useless extras, eventually even minimalistic
- normal watch size & weight & look
- preference for analog indications
- almost zero need of operation (butttons, etc)
meters:
- (dive) time (& preference to show date for normal use as watch)
- depth gauge meter
- eventually for non tech divers: Time until first deco stop (see 10)
how to achieve:
- purely mechanical approach:
(1) analog device as described by others, with normal indication of time
(2) analog depth gauge
(3) bezel
- electronic approach
outside the water:
(4) analog indication of time
(5) large digital indication of the date
(6) solar loading for batteries
(7) radio frequency triggered time setting
upon dive start:
(8) reset of minutes to zero and start counting dive time
(9) date display changes into depth meter mode
(10) set of hour indication to 55 minutes, used as a count down for time left until deco stop dive starts
(11) a light illuminates the watch