[QUOTE - I used to work on a boat dock. We referred to parts and tools dropped overboard as "on the aqua shelf". This is where I also fine tuned my theory that splash is directly inverse of cost. ]
So sorry, not so much on topic, but I can't resist -- one summer, we and friends rented two houseboats for touring Lake Powell (Utah), and when one boat developed engine trouble, the marina sent out a mechanic who worked on the engine where we were beached -- and he wore his tools on a chain around his neck. I'd never seen THAT before. But since the dropoff was hundreds of feet down, it made sense.
Agreed with everyone above -- need to cover the deck with something to catch parts and small tools.