Frank and Joe might be in over their heads when they discover an aquatic smuggling operation in this chilling Hardy Boys adventure--a fresh approach to a classic series. When Frank wins an internship at the Bayport Aquarium, he's stoked at the chance to t only earn school credit, but to also geek out about one of his favorite subjects--aquatic life. And his brother Joe is equally jazzed about taking scuba diving lessons from the super-cute instructor, Aly. But both boys' excitement comes screeching to a halt when the aquarium's most valuable asset goes missing: a rare two-hundred-pound sea turtle named Captain Hook. Frank and Joe stumble upon a network of underground tunnels hidden beneath Bayport...and realize the aquarium is a secret entry point. Could the aquarium be the newest target of a sinister aquatic smuggling ring? And can the boys snag the gang's mastermind before they end up in treacherous waters?