I know plenty of people who write off their boat's interest.
So far, only one of them has been audited.
His boat has a porta potty in a "separate potty room" - PASSED that test.
His boat has a cuddy that has a filler cushion that makes into a bed - PASSED that test.
Has a "clamp on" barbecue grill that fastens into a rod holder. Is stored on the boat and is accessible, alone with the propane bottle - PASSED that test.
Boat also has full canvas enclosure. Auditor said that if it had been an "open" boat with no enclosure, that he would have to have disallowed it. Never heard that part before.
I would take whatever advice your tax guy gives you.