The story of Merliah (Barbie), who made it to the finals of the surfing competition in Australia, has to face her biggest rival Kylie Morgan. After the competition, while Merliah is occupied by the media, the sneaky fish Alistar talks to Kylie and urges her to steal the magic necklace Merliah got from her mother Calissa. Kylie falls into a trap and frees the evil Eris, Calissa's sister, who wants to take over the sea land - Oceania. Merliah saves Kylie, and in the meantime, learns about the mermaid celebration. However, when he finds out about Eris' evil intentions, he decides to fight his aunt and has to say a poem, whether he likes it or not. Just saying the poem has no effect, only when Merliah swaps legs for a tail the spell begins to work. As a result, Eris loses the mermaid's tail and gets human legs and has to leave Oceania. Kylie and Merliah become close friends, and Merliah gives Kylie a necklace from Calissa as a gift. The main character turns the fish's tail back into its legs and takes part in the finals of the surfing competition.