Leave it in a nice warm spot. You can even stick it under a lamp to facilitate the evaporation quicker. Chances are, you won't have anything left to notice - if it was just rain water.

I had a friend dump her camera directly into a lake, where it sat for about 2 minutes while we tried to fish it out.

She left it with me, and within 48 hours I had it 100% functional again with NO visible watermarking and I did not have to disassemble it.