Bonnie finds Fynn hurt and unconscious on the beach at Crescent Island National Park. The only thing he seems to remember about his past is the dolphins bringing him to shore. But Fynn is hiding an incredible secret. He knows more about the surrounding waters - and the dolphins - than anyone could ever guess. When Bonnie accidentally discovers what he can do, she agrees to keep his special abilities a secret. So when dolphins and fish around the island start dying it's up to Fynn and Bonnie to find out why, and stop it if they can. Or one of Fynn's family could be the next to die...