Was recently submerged, would replacing the battery be the fix here?

Hard to tell without inspecting it inside. If water got in, the damage may involve other parts too. If it heats up beyond normal there’s quite likely something shorted there and letting current flow may just make things worse. Having someone with some skills in microsoldering have a look at it may be a good idea, especially if you really care about the watch for one or another reason. Economically I’m not sure it would be worth a repair.