Getting a mailing address is a piece of cake. Liz's apartment number approach is a great idea to make various forms work.
However, where you owes income or property taxes is based upon where you and your boat are actually located and for how long. I think most realize that using SBI not only doesn't make you a FL resident, it would be a pretty easy place for revenue agencies to check for potential cheats. With cell phone and credit card records, it takes any state about 24 hrs to determine if you've met their requirement for taxes due.
Ironically, paying local taxes without an address could be a challenge.
No, I am legally a Florida resident at SBI. It is my only legal residence.
State income tax is handled by filing a return in the state you earn the money in.
For example we still own real estate investments and our house in RI. We have to file a RI return for those monies earns in RI from rents and properties there and of course local authorities where the property is collect that tax always.
But most of our income is on our 1040 and FL does not have income tax so we do not file a return there for money earned through other means.
We have no physical location that we live at that is fixed, but we are legally FL residents.
If you live aboard in a permanent slip outside if FL SBI makes less sense, but if you move around a lot across multiple states then you can make residency in FL. If you work in different places as you travel from Maine to FL you are going to need to file state returns in each state for the income earned there to stay legal.