Mako Mermaids centers on three mermaids, Sirena, Nixie, and Lyla, who are assigned with the task of protecting their magical Mako Island from trespassers, only to be thwarted by the arrival of a 16 year old land-dweller Zac – who forms a special connection with the island and is granted a blue fish-like tail and amazing marine powers. Threatened by his existence, the mermaid pod are forced to move away, abandoning Sirena, Nixie, and Lyla, who in a bid for survival must get legs, venture onto land, and take back Zac's powers or risk being outcasts forever.