My wife handed me my sparkling set of keys the other day. They were in the thigh pocket of my cargo pants and had gone through the washer and dryer for their full cycles. To my amazement, both the key fob and the USB pen drive seem to be working flawlessly.
I did that twice with the key/fob for my smartcar. I was surprised each time that the key still worked. However, a couple of years later, my car started honking the horn whenever I pressed the lock/unlock button. The damage had been done, it just took a while for it to become apparent. To avoid my trouble, perhaps you might consider opening up your key and placing it in a jar with silica gel or even rice for a few days to get it nice and dry. It might not help, but at least you tried. If it does, it's better than replacing an expensive fob.
Washed my cell phone recently and mercedes keys recently. Don't ask. Phone definitely didn't work afterwards, even with hairdryer treatment. Keys seem to be fine.
There is a rubber seal in the FOB that prevents moisture from entering. It's expected to tolerate splashes and light submersion. I wouldn't take it SCUBA diving though, or intentionally go swimming with it!
