Mermaid Elle is princess of her kingdom in the warm waters of the Caribbean Sea. Her duty is to protect the ocean and keep her home and sea friends safe. Until one day, Gunk, a toxic creature who feeds off of the garbage in the ocean, shows up and causes catastrophic damage to her sea friends' reef. Now Mermaid Elle must find a way to stop this Gunk before he destroys the entire ocean. With the help of her new superpowers, a human girl, Sofia, and her loyal clownfish friend, Skippy, Mermaid Elle embarks on a mission to save her home and defeat the pollution monster.