While I use Airbnb, I would never consider being on the selling side unless it is a pure rental property (ie: in a popular area rented for most weeks of the year) for just this reason. Pretty much any non-commercial insurance is going to exclude
commercial uses and commercial insurance is too expensive if you just have an occasional rental.
I doubt you will find insurance willing to account for the idea it won't leave the
dock. It's just too small of a market. Also, it's way too easy for a non-boater to do something stupid and sink the boat (ie: not realizing it, they kill the
power to the
bilge pumps on the way out but leave the
water connected and a
water fitting fails)