Clutch squeak stops when wet?

So I just hosed down my undercarriage as I tend to most days after getting back from the beach. Unlike most days I decided to hop back into the truck and immediately noticed that my clutch squeak was gone. This lasted until the truck was dry again, and the squeak steadily returned during the end of that period.

Any ideas what that could be? When I push the pedal by hand I can feel it bind and vibrate just as the squeak starts, and the sound is pretty clearly coming from the other side of the firewall.

 

Really? no one knows?