When Captain Adamari falls into the sea during an attack on his ship, he is saved by Calypso, a mermaid from old sailors' tales. Suddenly, Adamari discovers he can bend water to his will. The mermaids believe his strange power can save them.

Meanwhile, the mighty kingdom of Atlantia is falling apart from within. Nobles fight against each other, the king's power weakens by the day, and whispers of rebellion echo through the streets. The Aurelian Kingdom watches from across the sea, ready to strike when Atlantia is at its weakest.

As war brews on all sides, Adamari just wants to get home to his family. But when Calypso finally shows him the truth beneath the waves, nothing will ever be the same..