The Oceanic computers are a PITA to change batteries correctly and not have flood. Best bet, if it's convenient, is to always take it to a reliable dealer, who does many and get them to do the swap. Also, the Oceanic gobble up batteries. If I'm taking a trip, have more than 12+ dives on the computer, and we have two,, I always get fresh batteries. Even if your screen shows a full charge of three bars, get fresh batteries. The power will drop very quickly. I like the simplicity of the Oceanic, but they have their flukes.