Blackrobes have costantly RULED that Boats and Motor Homes are "conveyances", not homes protected by our Bill of Rights",...just another example of "compelling State interests" conjured to enhance the police powers of the State.
It does not seem to matter that such dwellings are citizens' homes. One can always put such for as one's defense or cause of action, but don't bank on it. You'll be shot dead in the name of police action - in your home, even if you could have proven that you were not a criminal/terorist.
Boats have always been subject to boarding and search--they are, after all, operating on and across the borders of this country.