If it were me, I would not submerge my phone under water.
In order to repair the screen, the adhesive/waterproofing have to be removed from the front and the back of the phone. Its very possible that there could be leaks.
But then again...I would not submerge my phone in water no matter what. Even though it has a waterproof rating, Samsung does not warranty against water damage. Plus water damage is basically a death sentence for a phone. Pick up a cheap action camera for such things.