The longer a water damaged cell phone sits the less repairable it becomes. As time goes on the corrosion and rust eats away at the contact points on the board and even after just a couple weeks there is often nothing that we can do for it.
This is an iPhone 4S that was dropped in water and left sitting for a couple weeks. If we had been able to get at it right away and clean it up we may have been able to save it.