Goosebumps 19 - Deep Trouble

Siblings Billy and Sheena Deep are spending their summer vacation on the Caribbean island of Ilandra with their uncle named Dr. Deep. A zoo crew wants Dr. Deep to find and trap a mermaid that has been reported in the area. While swimming, Billy is almost killed by a hammerhead shark but is saved by the mermaid whom Dr. Deep traps in a large glass tank.