Ahoy there, Scooby! The famous dog detective and his mates are onboard an old-fashioned clipper ship. The captain, Skipper Joe, has just inherited the legendary pirate Tarwhistle's captain's hat. According to seafarer's lore, there's a treasure map inside. And it looks like a sinister deep-sea diver is after that treasure! Can Scooby and the gang solve the mystery... before the spooky diver makes them walk the plank?