"Not every floating structure is a 'vessel'," Breyer wrote for the majority. "To state the obvious, a wooden washtub, a plastic dishpan, a swimming platform on pontoons, a large fishing net, a door taken off its hinges, or Pinocchio (when inside the whale) are not 'vessels'."

http://news.yahoo.com/supreme-court-says-floating-home-not-vessel-154307160--finance.html