Scooby, Shaggy, and their friends are going to the aquarium to help clean the tanks. They're excited to swim with the sea turtles and octopuses, but an assistant at the aquarium warns them to be on their guard. According to legend, a ghost diver haunts the tanks searching for buried treasure, and tries to scare off anyone else who might find it. Zoinks! The gang straps on their scuba gear and dives in, and sure enough, the ghost diver attacks! It's time for Mystery Inc. to get to the bottom of this. Who is the ghost diver? Where is the buried treasure, and who put it there?