Been there, done that. You will likely need a new immobilizer. If you're at the dealer they will want to take the seats out to get the carpet out so it can dry. Not a bad idea to do that, just that it comes at the dealer's hourly rate. With a new immobilizer you may need new keys as well.
Two things. Check your front and rear drains so that this doesn't happen again.youi may want to follow this link
http://www.ecudoctors.com/
Other forum uses have recomended them before. If they can fix it you'll avoid the cost of reprogramming and new keys. An indie might go for this, not sure about a dealer.
And get your checkbook out.