Thora's no ordinary girl. She's got scales on her legs, purple feet, and a blowhole that squirts water from the top of her head. Thora's a half-mermaid, and as mermaid law commands, Thora must spend ten years at sea and ten years on land. In a houseboat called the Loki, Thora sails the seas with her mermaid mother, Halla, and her guardian, Mr. Walters. But when Thora returns to the seaside town of Grimli, where her father grew up, she encounters fat-cat tycoon Frooty de Mare, who will stop at nothing to expand his Tooty Frooty enterprises. With the help of new friends and her pet peacock, Cosmo, Thora has her work cut out thwarting Tooty's evil plans - not to mention doing a bit of exploring into her own Grimli roots. But, despite being half mermaid, this exceptional young heroine somehow always manages to land on her feet...