you can get just as good or better sound quality out of a single din cd player, and i doubt you are oging to be watching dvd's on the water. so unless you are using it, why bother?
some of those in dash video units have av inputs so its possible to watch video you are recording of your riders. I thought about putting it in my boat. I live in florida and getting caught in a downpour is a very likely event. Dual makes a 500 dollar unit which I belive is single din. I say give it a shot.