Foreign Flagged Yacht For Sale

I have a customer interested in one of those yachts you see advertised that says: "Not offered for sale to US residents while in US waters." What does that mean exactly and how does a buyer of such a yacht return it to US Documentation? I read where there is a 1.5% duty payabale. Should that tax be the responsibility of the Buyer or Seller? Does it make any sense for a new yacht owner to continue offshore registry if the intended use is 100% US on the Chesapeake Bay? If anyone has any insight on any of this or could point me in a good direction for the info, I would be grateful!