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.
Cleo discovers a comet is causing fish to flee the waters around Mako Island. The girls find a way to restart the message in the Moon Pool and discover the comet will collide with earth. Sophie meets Ryan and with Zane's help they join forces to remove the crystals from the Moon Pool.moreless
Don gets a second job at the Marine Park on the Pirate ship and outshines Cleo, threatening the future of her Dolphin show. Bella and Will find difficulty trying to connect with each others' interests.
Bella wishes to ask Will to come with her to the big party, but a misunderstanding ensues when it seems he's asking Rikki. Zane thinks Rikki has another date as well, Sophie wants to go with Zane, and pandomonium erupts. Sophie tries to get Zane to change the name of the cafe.moreless
The girls must face final exams and avoid a water attack in public when the full moon rises early. They receive a message about Mako when they go to confront the force in the Moon Pool.
Zane steals one of the Mako crystals in order to get Rikki's attention, but when the girls discover the immense energy inside of them, they have to find a way to rescue him.
Bella suddenly develops a sneezing allergy which triggers her powers. When Zane makes Sophie the head of the cafe, she looks to use Bella's problem as a way to get her and the band fired.
Will competes in the Free-Diving Championships and wins, but then decides to quit competing altogether. Meanwhile, Rikki ends her relationship with Zane when she sees Sophie and Zane kissing.
Rikki fears Ryan's explorations on Mako Island will uncover their secrets but Cleo and Bella discount her concern. She almost goes too far trying to stop Ryan from discovering the crystals in the Moon Pool.
Cleo meets Ryan, a geophysicist working for her stepmother Samantha, and asks him to take a look at the Mako crystal. Rikki is not happy that Cleo is seeking outside help, causing cracks on the girls' relationship. So Rikki starts spending all her time in the Moon Pool and discovers that her powers have strengthened after encountering the water tentacle. Finally Will confesses to Bella and Cleo what really happened at the Moon Pool, despite promising Rikki not tell the others.moreless
The girls decide to spend the next full moon at the café to avoid another water attack. Zane agrees to help them, but learning that Bella invited Will, he continues with his own plans and invites his friends to join. Angered by Zane's behaviour and frustrated by their inability to stop the water tentacle, Rikki decides to face the phenomenon alone and heads for Mako. Cleo and Bella are unable to follow her immediately, so Will rushes instead to protect her. But things doesn't turn out as planned.moreless
Sophie steals Bella's idea for a fund-raising concert and uses it as her own. Cleo must deal with high tensions when Samantha moves into the house.
Zane challenges Will to prove his skills as a free-diver, so Will pushes himself too far and looses consciousness deep in the water. Rikki comes to the rescue and performs CPR. That causes Will to show attraction towards Rikki. Also the girls discover a unique crystal in the rock from the moon pool that matches the crystal around Bella's next.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.
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.
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.
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.
To get more interest in the cafe, Zane develops a dirt bike race. However, Rikki finds out that it is a scam. She and Bella decide to team up to teach him a lesson. Meanwhile, Lewis and Cleo find out something interesting about mixing the waters in the Moon Pool.
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.
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.
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.