Zaldog, please don't mistake this as accuding you or anyone of trying to pull off anything. We'd all love to be able to 100% deduct boats--but that's not so easy. Regardless of what the boat is used for, if you are living on it--it is not used exclusively for business.
If I'm a videographer, over or under water, and I use my car to get to and from locations, sure that's a 100% legal business deduction for the business use of the car. And there are specific rates and percents that I'm allowed to take. If the car is used less than 51% (?) for business purposes I can't write off the car, or percents of the car. I can only write off business mileage at the business rate. And if the car is registered to the business (as many people used to lease cars "just" for their business) and the IRS looks at the mileage records, looks at me and says "But it is your only car, and your personal use has outweighed the business use" guess who will be disallowed the business deductions for the car, and then penalized for trying to get away with it?
With a boat, especially a boat you are living on, unless you can document all business use and establish that it is not your residence--you probably will be allowed to deduct only the cost of the
fuel your burned going to and from the locations. Unless the IRS has a "business boat mileage" rate, who knows.
This is an area where if you cannot afford to spend $100-200 with a tax CPA who is also an EA (Enrolled Agent with the IRS), you can't afford to entertain the idea of writing off the boat. ANYTHING "different" and "creative" and non-standard, attracts their attention. What people don't realize is that the IRS are in some ways sharper than the NSA or CIA. If you claim you own a diner or sandwich shop, they know exactly how many slices of bread, loaves of bread, slices of tomato and lettuce and pickle spears per sandwich, how many napkins, paper bags, and gallons of mayo the typical deli uses. All cross-referenced and percented.
You file a return that mysteriously don't match their percents--and that's an audit flag, because they know it is a cash business, infamous for cheating. And yes, they actually have gone into delis, buying lunch for a week and counting how many ounces of bologna or roast beef are on each sandwich.
But if you can find their rules--clear rules--that cover the use you want to follow, they'll let you do it. "My boat is strictly a business expense, I just sleep in the office" may not fly very well. < G >
The traditional, and fully IRS sanctioned, way to deduct your boat is to buy the boat, put it in formal charter service (hire a skipper or bareboat it, but also hire someone to bookthe charters and manage the boat), and BOOK IT YOURSELF AT THE USUAL PUBLIC RATES for your business trips. That way everything you spend is an arms-length transaction, and if you've done it right, you make money on the charter company as well. This is done, and sanctioned, for privately owned boats and aircraft alike. Any good CPA/EA should be familiar with how to set it up.