Absolutely Wrong
The USCG Documentation center makes very clear that Federal Documentation does NOT exempt you from EITHER State regulations, registration, or taxation. "State" meaning the State of your Documented "home port."Many (not all) States waive any additional State boat registration if your boat is Federally Documented. I don't know of any State that waives the taxation or enforcement of laws, however.There are generally multiple State/Local juristictions to deal with. Here in Massachusetts, you have to pay the one-time 5% Sales Tax to the State Dept. of Revenue, and pay the "home port" Town the annual depreciated-value-based Excise Tax. Also the Town Harbormaster gets the mooring fee.In Massachsetts, if you remain in local waters over 60 days you become liable for local taxes, too. Same type of rule applies to many other States. (A similar rule applies if you sail overseas to a European Union country.) Keep moving on!--Ron