Happens to everyone. It's embarrassing, but it happens.
Dry it off with a paper towel as much as you can, then stick it in a bag of dry rice overnight. The race absorbs the water inside the phone. Remove anything you can first though, like the backing or the battery, sim card, anything like that and put them in the bag separately.
Turn it on in the morning. From what I've seen it works about 70% of the time.