My objection to handicap spaces is that all too often they are used by people who are overeaters. I know of three people that have the handicap signs only because they are so big, that walking is a problem. Don't get me wrong, I also have a weight problem, but not one of them signs. For those people they should have to park farther from their destinations and could use the walk.
Now for the boats, I think if the boat deck is not level with the pier they are gonna have trouble no matter what. For the truley handicaped I would think a floating dock would be better for them. And how do you know one boat that is hancicaped from another? Simple put another decal on the bow! And a big blue H on the stern.
