If you have deck hardware not sealed it doesn't take too much rain to fill it up. I don't know the construction material on those but if they have wood up there it's probably soaked. pull everything out and put some fans in there for a while blowing air around. Once it's dry lay a bag of charcoal in there with the side cut open to absorb the funky smells. Store that thing under a roof next time.

story I always heard was after a lawsuit where someone died from generator exhaust getting in the cabin of a 38 they started sealing that bulkhead all the way to the bottom of the hull in anything with a cabin.