that happend to me, i had a razr, and it fell in the bathtub!
just take the battery and sims card out, and lay them out to dry for a day or so.
and everything should be fine, if not.
call your phone people.
You can't dry it out like you would any other phone because of the fact that you can't take out the iPhone's battery.
Just take out the Sim, try to get as much water as you can out manually, and then use a hairdryer on a low setting, and I mean /low/, to attempt to dry it off.
You can also leave it in front of a fan overnight, hope that helps.