I have a Oceanic Data 100 and the batteries in it are user replacable and I suspect his are as well. The port on mine is about the diameter of a quarter and is off center, there are 3 small holes in the body of the computer next to the round port. Just looking at the manual for the one I have and it shows that the words "Hand tighten" and "use coin only" are printed on the round access port for the Data 100 (too lazy to remove it from the console to look). The last time this was opened, it took a good bit of force. Mine uses (2) CR2032 (or DL2032) batteries. Don't over tighten it, put a little silicon grease on it and if the o-ring looks bad, replace it...on second thought, if it's a 93, replace it just for good measure.