Here is some info since i probably have used the gopro underwater more than most.
Patriot 16gb class 6
You do not need a 32gb because you cannot fill a 16gb card in one day.
You need about 3 batteries for 1 FULL day of diving. That means from 8am in the water till 5pm recording your every dive. I say the battery usually lasts about 4 hours. Although i do more dives than the average person per day.