Fins and Flippers

Misfit girl Josie Fletcher turns into a mermaid every night, and she hates it. So when she hears about the great city of Atlantis from a merman who washed up on her local beach she decides to go and visit. And blow it up if at all possible. Unfortunately for her, it turns out that someone else might just beat her to it. But joining forces with the bad guys is no big deal, right? Until she realises that being on the bad side has its disadvantages...