Barbie in A Mermaid Tale

Merliah Summers, a talented sixteen-year-old surfer, is participating in a surfing competition at Malibu Mavericks. During the event, her hair unexpectedly turns pink upon contact with seawater, startling her and causing concern about her appearance. She then dives underwater and encounters a dolphin named Zuma, who reveals she can breathe underwater and hints at her mermaid heritage.

Merliah confides in her grandfather about her strange pink hair and underwater encounter. He reveals that she is half-mermaid, born from her mother Calissa, the Queen of Oceana, and her human father Rip. This revelation explains her ability to breathe underwater and her unique hair color. Merliah learns her true identity and the danger posed by her mermaid nature.

Her grandfather explains that Calissa, Merliah's mother, hid her on land to protect her from her evil mermaid sister Eris, who seeks to take over Oceana. Calissa's concern was that Eris's ambitions could endanger Merliah, as the mermaid child lacked a tail and was vulnerable in Oceana. Merliah begins to believe she might have to return underwater to face her heritage.

Merliah throws her infant necklace in anger after initially doubting her mermaid identity. The necklace reveals that Calissa is still alive and implies she is a prisoner. Merliah realizes her mother is alive and decides to rescue her, igniting her desire to find the truth and save Oceana.

Merliah arrives in Oceana during the Eris Festival, an event controlled by her evil aunt Eris. She and Zuma hide to avoid detection and witness Eris's control over the ocean, which has weakened due to her rule. Merliah is scared but determined to find her mother and restore balance to the kingdom.

Merliah visits a boutique run by mermaids Kayla and Xylie, who help her appear more mermaid-like after her initial disguise. With their help, she begins to gather information and forms alliances with the Destinies, three mermaids with prophetic powers, who reveal that Calissa's daughter is already in Oceana and fighting to overthrow Eris.

Merliah, Zuma, and her allies seek three magical items necessary to defeat Eris: the Celestial Comb, a Dreamfish, and Eris's protective necklace. They travel to locations guarded by giant jellyfish, navigate currents to find the Dreamfish, and distract Eris to obtain her necklace, preparing for the final confrontation.

Eris spins a massive whirlpool in an attempt to destroy Merliah, who calls upon the Dreamfish for help. The Dreamfish offers to grant her a wish, but Merliah refuses, instead choosing to get a powerful mermaid tail. She ultimately destroys Eris's necklace, revealing her vulnerability and leading to Eris's downfall.

Eris is sucked into her own whirlpool and cast down to the deepest trench in the ocean, ending her reign of terror. Merliah frees her mother Calissa from captivity, restoring the rightful ruler of Oceana. Calissa grants Merliah her necklace, empowering her to switch between human and mermaid forms at will.

With her mind made up, Merliah returns to Malibu, wins her surfing competition, and celebrates her identity as both a human and a mermaid. Her adventure ends with her embracing her dual heritage, ready to balance her life between land and sea, and maintaining her role as Queen of the Waves.