A Citizen dive watch is a popular watch with scuba divers. Because the watches are sealed with a rubber "O" ring to keep water out, they're considered waterproof. They are also built to withstand the pressure that is created at deeper depths. Newer models offer a self-charging, renewable battery, but some models still require a change of battery. It is best to have a professional change the battery, to make sure the seal is tight and to test for pressure resistance, but you can change it yourself using a few simple tools.
Place the watch face down on the clean cloth. This will ensure the face isn't scratched if moved.
Remove the screws with the screwdriver and take off the back plate or pry off the back of the watch using a knife if there are no screws. There are notches in the back where you can insert the knife. Be careful not to damage the "O" ring gasket behind the back plate.
Remove the "O" ring gasket with the tweezers.
Remove the battery, or batteries, if your model has more than one. Note how they are placed with regard to the "+" and "-" poles, so you can be sure to place the new battery in the same way.
Put the new battery, or batteries, in the watch. Make sure the watch is running by checking the watch face. If not, then make sure you have the battery, or batteries, in the correct way. If the watch still isn't working, something might be wrong with the new batteries or with the watch itself.
Put a small, thin layer of silicon sealant around the gasket and place it back in the watch, using the tweezers.
Replace the back plate. Put the screws back in, if there were any, and tighten them.
Replace the rubber gasket if it is brittle and worn.
Replacing the battery, or batteries, by yourself voids the warranty.