Water resistant watches are designed to keep water out of the watch case. There are gaskets underneath the watch case backs that seal off the inner camber, protecting the watch movements from contact with air and water. Watch manufacturers advise taking water resistant models to professionals for battery replacement. With the right tools and instructions, you can replace the batteries and reseal the case back with a new gasket.
Place the watch case into a watch case holding vise. Alternatively, you can lay the watch face down onto a rubberized mat to prevent slippage while working.
Open the watch case back. Water resistant watches have case backs with notches around the rim. Attach the case wrench over the watch case back. Tighten the mechanism on the wrench until its pins are aligned with the notches in the watch case. Turn the tool counter-clockwise while pressing down slightly to loosen the case back.
Alternatively, find a pair of needle nose pliers that will fit into two of the notches. Align the tool's arms with the notches in the case back and turn counter-clockwise, pressing down slightly to prevent the plies from slipping.
Remove the watch case back and lay it on a clean cloth. Take note of how the gasket, a small rubber o-ring, is positioned inside the watch. Remove the gasket with the plastic tweezers and lay it on the clean cloth.
Remove the battery clip. Clips lay over the batteries and hold them in place. Your watch can hold its batteries in place by one of three systems.
For spring clips, lift one end of the metal spring clip up with the tweezers. The clip will come out of place and allow you to reach the battery.
For screw-on clips, use the small screwdriver to unscrew the screws holding the metal clip in place. Remove the clip with the tweezers.
Permanent clips look like spring clips, but cannot be removed from the watch. To access the battery, lift a corner of the clip up with the screwdriver and remove the battery using plastic tweezers.
Regardless of the clip style, note the position of the battery before removing it. The new battery must be reinstalled in exactly the same way.
Using plastic tweezers or cotton gloves, gently replace the battery in its appropriate mount. Reinstall the clip using the opposite procedure you used to remove it.
Reinstall or replace the gasket. Check if your watch gasket is in good condition. If it has cracks or splits running through the rubber it should be replaced. Rub a thin layer of silicone over the gasket and place it in the watch as before.
Replace the watch case back. Use the watch wrench or pliers to turn the watch case back clockwise. Continue tightening until the case back is turned as tightly as possible.