If the phone is ruined and water damaged. Before you take it In. Clean the battery terminal And take it apart and clean all the corrosion off the circuits if they don't visibly see corrosion they will replace it, and you don't. have to lie just say it doesn't work. WD 40 and a tooth brush works.
The guy who answered above me is right, but crack it open so the silica can absorb the moisture inside the phone, before major damage can be done. Personally though, you can't do anything, just get a new phone.
Put regular rice in a bowl and put your phone in the bowl, the rice will absorb all the water... Worked at AT&T for along time we always had customers with the same problem you can also try leaving by some sun shine not too long
Assuming that your phone has just dropped in water, turn it off and make ensure that you do not charge it; charging will short circuit your phone. Remove the battery and its cover and then cover your phone in a bowl of rice as it helps soak up moisture. The next step is to draw it away using a vacuum cleaner; hold it for up to 20 minutes. Your phone will be just as ?new?.