Three very different teenage girls, Emma, Cleo and Rikki, facing everyday teenage problems. With a twist: they're mermaids; after discovering a magic place where they are given incredible powers over water that change their lives forever.

Annoying Miss Popularity, Miriam, is having a pool party and the girls want to go. But being around water is risky, especially when Zane tosses Cleo into the pool. Lewis is the only one around to help so he finds out their secret.

Rikki, Emma and Cleo discover that sea turtles are being captured by fishing nets. When Rikki and Emma attempt to rescue the turtles by cutting the nets, it causes the fisherman to think that there is a rogue shark roaming their ocean.

Emma decides that she is not going to have her annual sleepover party due to what has happened to them. But Rikki and Cleo try to convince her otherwise. Meanwhile, Lewis conducts experiments on the girls.

Emma gets into trouble babysitting her little brother Elliot. She goes to Lewis for help when Elliot develops a crush on Rikki.

Rikki is offered a job to collect rare fish. At first it seems perfectly fine, until she finds out the person that hired her is selling the fish for large profits.

Rikki enters a short film contest on the theme of 'Heroes' and decides to capture some nice underwater footage with her 'abilities'. Meanwhile, Emma is interviewing her mum and Zane and Lewis are planning to rennact Dr. Bennet's windsurfing record.

The full moon gives Cleo a power to put guys in a 'trance' and she suddenly gets a rush of admirers.

Cleo's 16th birthday is approaching and she thinks that her father is going to throw another embarrasing birthday party. Meanwhile, Zane tries to find the 'sea monster' that he saw when he almost drowned.