The Landon family is Southbound—headed for Florida to investigate a mysterious illness plaguing endangered manatees in Everglades National Park. Jack, Ashley, and their friend Bridger soon find themselves in deadly waters with a seven-foot shark, an injured manatee—and a mystery to solve. Who was the stranger in the speedboat who snatched Jack's camera? And what does he have to do with the manatees? Join the heart-stopping chase through a maze of mangrove islands to find out!