A water resistant watch usually has a back that screws into the case and seals with a rubber O ring.
Sometimes the back can be very tight to unscrew so even with the dedicated wrench it is difficult to remove without damage to the case. The professional would disconnect one end of the bracelet and clamp the case into a special holder.
Once a non-dealer has replaced the battery it is usual to discover the back isn't replaced as tightly as original - this is reflected by the usual warning the watch will no longer be waterproof. The only way to retain the waterproof or water resistant quality is to have the battery replaced by a dealer or manufacturer when it will be, if required, pressure tested.
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A water resistant watch usually has a back that screws into the case and seals with a rubber O ring.
Sometimes the back can be very tight to unscrew so even with the dedicated wrench it is difficult to remove without damage to the case. The professional would disconnect one end of the bracelet and clamp the case into a special holder.
Once a non-dealer has replaced the battery it is usual to discover the back isn't replaced as tightly as original - this is reflected by the usual warning the watch will no longer be waterproof. The only way to retain the waterproof or water resistant quality is to have the battery replaced by a dealer or manufacturer when it will be, if required, pressure tested.