Merliah Summers (Barbie) is a top surfer at Malibu and is nicknamed, "Queen of the Waves". On the day of a surfing competition, Merliah is surfing mavericks, when one part of her hair suddenly turns pink on contact with seawater. Nervous of showing everyone her hair, she dives underwater and meets a pink-ish purple coloured, dolphin named Zuma. Merliah finds out she can breathe underwater. After telling her grandfather what happened, Merliah finds out that she is half-mermaid.