Oliva has a secret. She's a mermaid, and the daughter of Rita Santos, who has been cast out of her pod and lived on land ever since. While on a swim she meets three other mermaids; Serena, Nixie, and Lyla. They tell her that a land boy fell into the moon pool and they were cast out of their pod as a result. Who fell in to the moon pool? Read more to find out.