For as long as Alex Neptune can remember, the ocean has been trying to kill him. So he's not too happy when a bunch of sea creatures drag him to the abandoned aquarium on the hill, where an imprisoned water dragon needs his help. But how can he say no to a magical myth?

Recruiting his tech-genius best friend Zoey, legend-lover Anil, a sharp-shooting octopus, four acrobatic otters and a thieving seagull, Alex plots a heist to break the dragon out. And suddenly discovers the power of the ocean at his fingertips...