Kayla and Xylie give Merliah an outfit to hide her legs, and together they visit the Destinies, three mermaids with prophetic powers. The Destinies tell Merliah that she needs to collect three items in order to succeed in overthrowing Eris: the Celestial Comb, a Dreamfish and Eris' protective necklace. The group search for the items, occasionally calling Fallon and Hadley for help with research. They find the Celestial Comb in an underwater cave and the Dreamfish in the Adenato currents. In order to obtain Eris' necklace, Merliah, Kayla, and Xylie approach Eris, performing a song and dance to distract her long enough for Merliah to grab Eris' necklace, but soon has her mermaid tail pulled off, revealing her legs. In a rage, Eris creates a whirlpool to banish Merliah to the deepest depths of the ocean. While inside the whirlpool, Merliah calls the Dreamfish for help. The Dreamfish offers to grant Merliah's deepest wish and send her back to Malibu and erase her mermaid half for good. Merliah rejects the wish and accepts her responsibility as the princess of Oceana. Due to this, Merliah is given a real mermaid tail, which she uses to escape the whirlpool herself. Merliah reveals her identity to the people of Oceana, proving her identity by brandishing the Celestial Comb. Eris rushes Merliah, and after a chase, Merliah is able to lure Eris into the whirlpool. Eris is trapped and sent into the deepest depths of the ocean. Merliah finds and sets Calissa free. Calissa is queen again and makes Oceana healthy once more. In the aftermath, Merliah confesses that she misses her life as a human, and Calissa gives her a magical necklace that enables her to be a human or mermaid whenever she wishes. Merliah then returns to land, where she is reunited with her grandfather and wins the surfing competition.