When sixteen year old Zac Blakely decides to camp on Mako Island, unaware that three mermaids, Sirena, Nixie and Lyla, who are guardians of the island, are watching him. That night, when the full moon rises, Zac comes into contact with the magic water of the Moon Pool. The following morning, he wakes up discovering he has become a merman with a fish-like tail and the ability to control and manipulate water. His new found merman abilities will cause problems for the mermaids. The mermaids have been left behind at Mako Island while the Pod has left. Unfortunately they don't stop Zac from showing him his tail and powers.