The Flute of Sailroc Edifiice

An entry in the tenfootpole Wavestone Keep contest! From the publishers blurb: Characters obtain a magical flute that causes a tower to sail on a rocky island from the ocean. There is a lot of filthy lucre inside, but much of it is bulky, brittle, puzzling, or dangerous. When the tower starts sailing off, the player characters will need to devise a plan to get the treasure out before the tower leaves for good.