Galen, prince of the Syrena, is sent to land to find a girl he's heard can communicate with fish. He finds Emma and after several encounters, including a deadly one with a shark, Galen becomes convinced Emma holds the key to his kingdom.

When Emma's grandfather, the Poseidon king, suggests she and her Syrena love, Galen, visit a small town called Neptune, they find themselves in the middle of a power struggle that threatens not only their love but their ocean kingdoms.