Well, as far as living aboard and what the neighbors think, I have no clue.
BUT. As far as nooky on a boat... I have a friend that does deliveries w/ his girlfriend (they are boat captains) He was telling me about a delivery from the islands to FLA on a catamaran and it was off the wind all the way. Made for nude sunbathing and romps on the trampoline all hours of the day the whole way to FLA.
And I know of a certain "Admiral" (in training) who was checking out the aft cabins on boats at the boat show to see how much, ummm, room there was.

Even laid down on the aft berth and put her feet up on the "ceiling" (cockpit sole) to make certain it was comfy.
Now that's MY kind of Admiral!
Oh, and hi TWISTY! Welcome aboard.