1983 Scottsdale, washed it and now nothing

[chevyman95]

Craaaap, Was trying to get this truck cleaned up and I was spraying out the underside with a pressure washer, finished and cranked it up and moved it out of the yard. Went back 5 minutes later and turned the key to the on position and the dash lit up but wouldn't crank then the dash lights went out and now I have no power nothing. Tried to jump it and cleaned the terminals but still nothing. Where do I go from here? Thanks