Any “navigable waters” fall under this jurisdiction which at a minimum includes all salt water and the Great Lakes, plus a few other odds and ends rivers and so forth. Indeed, almost all state and landside federal law goes out the window on a boat - a frequently bumped into example by boaters here in Washington is getting a civil penalty flavored reminder from USCG that cannabis is still (for whatever reasons) federally an illegal substance, and having it on a boat at all is an offense (with larger amounts or future violations escalating as far as seizure of the vessel).

Marine laws are nuts.