Lewis discovers that the girls are mermaids but promises to keep their secret.
Emma and Rikki use their new-found abilities to free hatchling sea turtles caught in fishing nets.
But when they shred one of the nets with a knife, they spark stories of sharks patrolling the waters.
Meanwhile, Emma and Rikki have bad news for Cleo; the fishing boat that caught the turtle in its net was her father's.
After being rescued the girls return to their normal lives but soon discover they have changed: seconds after contact with water they transform into mermaids.
After further experimentation, they discover they also have unique supernatural powers over water.
The girls meet Louise Chatham (Christine Amor), an older woman who reveals that she too was once a mermaid.