Frank and Joe can't wait for their trip to the Bayport Aquarium. A new tide pool exhibit has just opened where visitors can learn all about horseshoe crabs, rays, jellyfish, and other sea life as they touch and hold the flora and fauna that make up the aquatic ecosystem!

But in the middle of the presentation, an aquarium worker realizes that one of the creatures has gone missing from the tank. It can't survive for long outside the water, and the clock is ticking.

Can the Hardy Boys follow the clues and find the culprit before the new exhibit sinks?