Well, I don't really know if you should call it discharging. In my lifetime I dropped 3 phones in the water, n82, n97 and (unfortunatly) a n900. In all cases, the battery was full (or at least enough power in it), but once I took it out the water, let it dry, and boot it up, it was empty and needed to be charged in order to work. So my conclusion was: It drains when you drop it in water!

Oh and for the record, they all worked fine until they mysteriously (and gradually) broke down after a couple of weeks. Probably rust...