Poida said..
only a problem when you get audited.
how much work related things are you doing with the boat 50%? 5%, 90%, some sort of proof of it?
the stonemasons had a party boat at mandurah when they were doing the canals, im sure they claimed the parties and boat as work related?
In a case like that, if its only used for work related issues you'd be okay. But if you used it privately at all, you'd need to run a log book and the cost would then be prorated.
Even owning a boat yard, its was difficult..
But as has been said, you can claim anything, its just surviving the audit thats will be your problem

Boats and taxes, send up flags in the Tax department..