Sophie and Ryan damage the Moon Pool in their efforts to obtain the rare crystals. The girls improvise and use their own magic to prevent the impact of the comet and a planet wide catastrophe. Rikki, Cleo and Bella graduate with a surprise.moreless
Don and Sam get married and Lewis gets a scholarship to the American marine biology institute and has to find a way to tell Cleo that he wants to go.
It's Rikki's birthday, and despite Chleo's and Bella's lovely Gift, Rikki's disappointed that her own boyfriend, Zane seems to have forgotten. Meanwhile, at the café Sophie feels like she's missing something, while her brother, Will, tries to talk to Bella, but she continues to reject him. Then, when a shady person living on a Mysterious boat pays the Café with counterfeit money (while Sophie does her snooping), Rikki confronts them and lands herself in trouble, therefore giving her the most dangerous and probably strangest birthday ever.moreless
Bella almost gets caught by Sophie while swimming with Will at the public pool. She realises that Will is interested in her as a mermaid rather than her as a girl and decides to stay away from him. Meanwhile Cleo helps Rikki at her café.moreless
Will is getting closer to Bella, and her secret and when he starts to bug her about Makko, Chleo and Rikki tell Bella to keep away from Will, which is hard for her because she finally feels their relationship is blossoming. But when she finds out that Will really is on the lead, she has no choice but to end it with Will. But unfortunately he wont let go that easy, and tricks her, revealing her secret. But only hers, not Chleo's and Rikki's. She tells him the story, and this doesn't go down well with Rikki, but all is calm again when Will swears to secrecy. Finally, Bella thinks they can have a REAL relationship.moreless
Cleo wants to experiment with the gravity defying water they created from the Moon Pool, but Lewis is against it. So she uses her father to get him out of the way. While Lewis and Don are playing golf, she invites the girls over to do some tests. But when Rikki accidentally gets the magic water into Cleo aquarium, Cleo's favourite fish Hector becomes suspended in a floating bubble of water. And when it turns out that the floating bubble has a mind of its own, girls are having trouble catching it. To make things worse Will sees Bella using her powers to retrieve the bubble.moreless
The girls are planning a sleepover to protect themselves from the water tentacle. But when Will visits, Bella is kidnapped by the water tentacle and taken to Mako Island. The girls go after her to try to safe her.moreless
On a trip to the beach, Don misunderstands Cleo's actions and thinks that it's better to call off his relationship with Sam. Elsewhere Will's sister Sophie tries to get a job at the cafe, much to Bella's dismay, as she sets her sights on Zane.moreless
Bella tries to get close to Will but when Bella goes to his place she sees him with another girl. Meanwhile Lewis tries to test the water from the moon pool but gets caught by his teacher.moreless
Cleo has to put off Lewis' romance plans in order to help Kim with her crazy love life. Meanwhile, Don meets up with a National Parks Manager, Samantha, and the two decide to date.moreless
At the marine park, Cleo seeks a job as a dolphin trainer. Meanwhile, until she and Bella reach an understanding, Rikki fires Nate's band, preventing them from playing in the cafe.
With Will finding out about Mako Island, Bella tries to misdirect his search so that he will not discover the Moon Pool. However, Lewis and the girls find out that the Moon Pool is different.moreless
Cleo and Rikki enter their final year of high school. They make friends with a new girl, Bella, and a new boy, Will. However, they encounter a new force on Mako Island that has the power to turn water against the girls.moreless