Charlotte and Mia have to grant four watery wishes to save the home of their mermaid friends! Tanesha has moved to a seaside town where all the other kids love snorkeling and surfing - and Tanesha doesn't know how. She wishes she could join in! Can Mia and Charlotte teach Georgie how to have seaside fun, and grant another wish? Or will Princess Poison turn up to ruin the day...