Turn it off and leave it off. Turn it upside down. Put it in a warmish place. An airing cupboard (for example) is a fairly good place to put it. Leave it 2-3 days then turn it back on. If it works you've been very lucky. However don't be surprised if after a day/month/year it suddenly stops working again. Water and electronics don't play nicely as you know and at the very least there may be some corrosion somewhere.
If after 2-3 days drying out it does not switch on or if it does it does not work as you know it should, then book an appointment asap at your nearest Apple Store/Apple Repair Centre for diagnosis and repair. Expect the repair costs to be steep as accidental/wilful damage is not covered by the Warranty unless you purchased AppleCare + previously. Actually I'm not sure you can get AppleCare + for non iOS devices?
Finally your data on the hard drive should be safe and it's a simple procedure to remove it, insert it into a drive caddy and attach it to another computer so you can access it.
Now what's your XServe/Server question?