I guess that the water got into the device and there was a short circuit because of that. I guess that you've fried your USB port. I'd get it on a warranty and prey that they would accept it. If they don't then either replace it yourself or get it on repairs. Authorized Sony service is one of the best I guess, but do read the opinions about a particular service because there are many different services.
My work on xda and things I'm proud of:
Single link for that as the sig got too big ^^
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sooner or later :P