The big trick is dealing with the pressure transducer. Most dive computers turn on/off at about 5-7 feet. You could set it up as a data logger sampling every second, but that will require a lot of memory, like more than the device has, so additional memory will be needed. It would also need to be either dumped directly or dumped to a removable storage device for anaylsis on a computer. Lithium rechargable batteries will keep things small, BUT they don't get along with water very well like sodium or potassium, and must be well sealed. Trying to keep things small, it would be best to have a dedicated circuit board for everything, and not try to add to an existing board.

Good idea for mers, UW hockey, and snorkeling use!