There isn't enough voltage at the battery to pass any signifigant current through the water. Don't worry about getting it wet.

I warm the engine slightly first, not fully hot, then spray foamy engine cleaner, mostly on the valve covers and intake. Any really dirty parts I scrub with a toothbrush. rinse it off, and start the engine immediatly to drive off any remaining moisture. Once dry wax any painted surfaces.

John C.