clean your bays with water no probs, as already said, a bit of water aint gonna hurt the engine but still cover the electrics with plastic, and you defo dont want water going into the open Alternater.
The worst, and imo a no no is Jet washing, water under pressure is gonna find its way into places you dont want it to go, and just cos you chance your arm and jet wash the engine and got away with it once or twice.... the electrical components in there are not water proof and will dead short with a bit of water, at least cover em with plastic guys.