I am going through this now and Delmarrey is correct - the USCG said it falls to the states laws. There is a provision that if it is used to transport crew to shore and back IN CONSTANT SIGHT OF THE YACHT it may be exempt but spending time ashore is not included. In
Maryland, and many other states, if the vessel is used in that state for a specific period of time you will pay a use tax on it - but many are reciprocal with other states sales tax so paying the sales tax at
registration avoids a use tax in another state. DNR just notified several slip holders at our marina last year who registered in Delawre to avoid
taxes and rented a slip for six months in
Maryland. One way or another it seems you will pay the
government to use your toy.