There are three mermaid: Serena, Nixie and Lyla, who are living in their magical Mako Island. Their duty is protecting the island from trespassers. One day, a teenage boy named Zac goes camping in Mako Island and he accidentally discover his specail ability in controling water. Later, he finds that he become a mermaid with a fish - like tail. Because of the existance of Zac, three mermaids are forced to move away. They must venture onto land, take back Zac's power or risk of being outcasts forever.