Its important to immediately remove the battery so the circuit has no power (to stop electrolytic corrosion) and get its interior as dry as possible as soon as possible to minimise damage. Although freezing it to -20 deg C would slow down corrosion, you risk it destroying the LCD, and popping off or cracking any components on its PCB that have a lot of water trapped under them.
As Rerouter said, go to a jewellers that does watch batteries as soon as possible, preferably as soon as you read this, ask them to open it, remove the battery, and give it back to you with the case open. However *DON'T* have them put the new battery in!
If the water was salty or heavily contaminated, odds are its going to need manufacturer's service or be BER. The longer you wait to get it dried out and the saltier the water, the lower your odds of success.