The kind I described, that are actually vessels as defined by the CFR: used or capable of being used as transportation upon the waters of the United States.

And then there are permanently moored floating structures that would be real houses if they were on foundations on land instead of afloat at the shore...the house in "Sleepless in Seattle" is one of those. They're not vessels...and therefore not subject to CG regs or any other laws pertaining to vessels. Instead of generators and holding tanks, they're connected to the local power grid and sewer system. The owners of those don't HAVE to pretend they own a boat 'cuz they don't!