This instructable will cover two ways that can help you repair a "wet" phone. As water damage varies from case to case, there is no guarantees that this will work in your case, but it is worth a try!
It is important to know that these procedures will NOT void warranty. However, if your phone has been water damaged, there is a large chance your warranty is already void! On newer phones, there is usually a sticker in the battery bay that is used to tell the manufacturer when a phone has been "water damaged" which allows the manufacturer to then cancel the warranty. This sticker is usually round in shape, and starts off white when it is not wet. Although, I think my samsung a900M started with brown and went to black.
If neither of these methods work, and your sticker is still it's original color, try to have your phone serviced under warranty.
CAUTION: Before attempting ANY method in this instructable, remove the battery, battery door, and SIM card if applicable, and place them in a safe location!
DISCLAIMER: I am not responsible for any damages to your phone as a result of you attempting any of these methods, do so at your own risk.
Step 1: Understanding the problem
When your phone got wet, it most likely got some moisture trapped inside it. This moisture causes the phone to behave very funny, and possibly not even power up.
This is due to the conductivity of water (It's ability to have electrical current pass through it.) This moisture can bridge certain connections in your phone, causing these behaviors.
Even though your phone may behave fine at first, it is better to dry the phone before use anyways, as the water that remains inside can be moved around, and cause issues later.
So what to remember, is that after exposing your phone to moisture, you want to nullify the moisture inside.