Saban's Adventures of the Little Mermaid (1991)

In this Japanese/French anime series, we follow the many adventures of Marina, who first wanted to be human under "Hedwig" the sea hag's spell. After her spell breaks, due to a snotty princess going after Prince Justin, Anselm the wise man and his wise otter, Ridley tells him the whole story and gives him tonic, so he can explore underwater. There, we hear the legend about a golden scroll that can change mermanoids to humans and live forever and also to re-unite humans and mermanoids. But the problem is, Hedwig and her ditsy shark friend, Dudley are going after them, no matter where they go. But if that's not enough, a spoiled nobleman wants to exploit the mermanoid folks. Will Marina and her friends fight the odds?