It received some water.
Disconnect it.
Drain all the water you can by tilting it.
Open the case.
Soak up all the water you can.
Place it in a box and fill it with rice. The rice will absorb any remaining water. Leave it that way overnight, or longer if you can, like 1 or 2 days.
(that's a recomended way to dry any electronic devices)
Open it to show any circuit board and electric connectors.
One by one, carefully disconnect a connector and preconnect it in exactly the same location and position a few times.
Repeat with every connectors.
This will rub off the corosion from the contacts.
Close the casing.
Plug it back and try it
Make sure that it won't get wet in the futire. Placing a plastic cover over it when not in use is a good way.
Try to locate from where that water came. If needed, call a plumber (broken water pipe) or a roofer (leaking roof).
Electro, April 2013
