Replacing the battery

It should be restored to the factory water resistance standard with any service that Apple or an AASP does where the screen is removed. A new adhesive seal is supposed to be used each time, and it will be checked with a calibration and mechanical integrity tester,

It was never waterproof to begin with. It is water and splash resistant.

You should never intentionally expose it to liquid and should certainly not intentionally submerge it.