Readers familiar with Rodgers' previous mysteries will find familiar elements in this routine, although action-packed, thriller. The protagonists are again a plucky boy-girl team and are again accompanied by an equally plucky dog, who's here introduced in an opening chapter during which a French couple (who then disappear from the story) are attacked in their boat by a mysterious sea monster; they escape and the dog is thrown from the boat. He joins Jeff Collins, daughter of an engineer in charge of a harbor dredging project on a Caribbean island, and Ben Jackson, who is seeing the world in his trimaran, as they attempt to discover what's behind the haunting of Mayan ruins on the island and whether or not there is a monster--a personal search, as a similar creature has attacked Jeff. The answers are not discovered before several scary chase scenes occur above and below water. The plot is believable, the action involving, but the characters are cardboard and the love story of the college-age protagonists predictable, including a couple of coy nude scenes. Any TV watcher will spot the villains immediately. In sum, effective but average escapist fare.