Ningyohime Marina no Bouken  

Sabans Adventures of the Little Mermaid, Ningyo-hime Marina no Bouken, Mermaid Princess: Marinas Adventure, 人魚姫 マリーナの冒険, Saban's Adventures of the Little Mermaid

In summary, Marina is a mermaid who falls in love with Prince Justin, a human prince from a kingdom on land. She saves him from drowning after he's pursued by a Cyclops and attacked by a three-headed sea serpent during a shipwreck. To win his affection, she makes a deal with Hedwig the sea witch to become human temporarily. Despite their growing bond, Justin mistakenly believes that Princess Cecily saved him from drowning, leading to an engagement proposal. However, he eventually remembers Marina's heroics and they continue to meet secretly while dealing with Hedwigs plans for world domination and Cecilys attempts to force him into marriage. They are aided by their underwater friends, Winnie the seahorse, Bobo the tropical fish, Ridley the sea otter, Anselm the wizard, and Chauncey, Justin's page.