The plan is to use the fin markers to show where sharks are lurking around the table. They will be attracted by any movement in the water. The head will be used for a shark attack. It is yet to be appropriately named.
As for the "son of kraken" ... well you sometimes just get lucky and buy something that needs no effort. He'll be dragging adventurers to their doom from ships, islands and in the water in no time at all.