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.

Cleo's sister Kim finds her diary and thinks that Cleo and her friends are 'evil mermaids' and she plans to tell everyone. Meanwhile, Lewis goes to Mako Island to find out more about what happened to the girls.

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

Miss Chatham gives Cleo a warning that she doesn't quite understand. Until Emma finds herself in a trance and unable to change back from a mermaid under a full moon.

Lewis is offered a great job with a marine biologist, but the girls are concerned that his interest will cause him to reveal too much information

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.

Byron asks Emma for help with training the school's swimming team and Emma has some trouble deciding whether or not to help out in her current situation. Meanwhile, Lewis continues to experiment on the girls, which annoys Rikki.

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

Emma invites Miss Chathams to stay at her place and Zane overhears Miss Chathams concerning about 'her treasure'.

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.

Emma is doing well at her new job at the JuiceNet cafe, but when she is left in charge, she has trouble managing her new employee, Rikki.

Rumour has it that Cleo has a boyfriend and her friends and family are trying to find out who he is. Meanwhile, Zane continues his search for the 'sea monster' he saw.

The girls have to fake sick as a result of a thunderstorm, so their secret won't be discovered at school. But their 'sickness' attracts the attention of doctors.

Zane's quest to find the 'sea monster' has led him to Mako Island. Rikki loses control of her powers as a result of the full moon and Zane finds her.

Cleo and Kim are stuck with their cousin Angela who wants to go body boarding and causes a bird brained distraction when Cleo refuses.

Lewis enters the annual fishing derby. When Cleo sees him struggling, she decides to help him out with disastorous consequnces. Meanwhile, Rikki and Zane are trapped on a hotel balcony.

Emma decides to change her look by colouring her hair red. Though nothing is that simple when you're half-mermaid. Zane asks Rikki out on a date.

Emma and Cleo are concerned about Rikki going out with Zane. They force Rikki to decide to either be with Zane or with them.

Rikki finds a locket that looks the same as Miss Chatham's in a Jewellery shop and she is determined to get it.

With the school dance coming up, Emma and Cleo hope Byron and Lewis will ask them out. Meanwhile, Miss Chatham and Lewis are arguing about which is more important, magic and science.

It's time for Emma's family's annual vacation trip, but she can't go as the risks are too high. But all her excuses don't go very well with her family. Meanwhile, with the return of Dr. Denman, Zane is closer than ever to cracking the girl's secret.

With Cleo's parents now divorced, Cleo is ordered by her dad to take more care of Kim, starting with taking her to a concert. But on the night, Cleo, Rikki and Emma all accidentally see the full moon, and take off to Mako Island, with Lewis in hot pursuit. Once there, the girls undergo another magical transformation in the Moon Pool, as a rare planetary alignment intensifies the power of the full moon – Emma's power is enhanced so that she can produce snow and frost, Rikki can conjure lightning, and Cleo can now control wind as well as water. After the moonstruck girls nearly harm Lewis, they realise that they must work to control their new powers, before anyone else gets hurt.

The girls have problems with their new powers and Cleo finds that Lewis isn't helping. A new girl called Charlotte arrives and develops a crush on a certain charecter

Rikki tries to avoid Zane when he comes back, but needs his help after an incident with a speedboat. Meanwhile, Charlotte continues to flirt with Lewis and Cleo worries for their secret.

Trouble arises when Emma throws a party to prove she is as fun as Rikki. Meanwhile, Lewis is trying to prove his manhood and Cleo is recieving cards from a secret admirer

Trouble is in the air as the Setori's start to suffer and the JuiceNet is endangered by a new bar. But when Lewis finds a book of mermaid spells, the girls attempt to use a potion to fix everything. However, things aren't so easy when you have special powers.

Cleo is worried when she sees her dad around with another woman. When she arrives at their house, she turns out to be Charlotte's mother! Meanwhile, Rikki and Emma attempt to save the Sertori's dinner with their powers.

Everyone is shocked when Cleo is fired at the Ice Cream Stand, and even more so when Lewis takes her place! Rikki and Emma strike back at him but end up going too far

Zane is curious by Rikki's reluctancy to reveal where she lives. So one day, he eventually convinces her to reveal her home: a trailer park with her grouchy father.

Emma has to take Eliot for horse riding lessons and the competitive perfectionist tries to be better than the instructor. Meanwhile, Lewis double dates with Charlotte and Cleo.

Cleo starts to struggle at school and gets help from the new tutor. But there are bigger problems when Charlotte starts to get closer to Mako Island with the help of Lewis.

In need of cash, Rikki decides to go and searching for a lost statue with a huge reward. But she lies to Emma and Cleo, which causes danger when Rikki is knocked out!

Emma gets poisioned after cutting her finger on some coral and she begins to turn into a white scaled monster! Meanwhile Charlotte thinks Cleo is trying to break her and Lewis apart.

On the night of a full moon, Lewis, Emma, Rikki and Charlotte accompany Cleo's family for a camping trip at Mako. When all three girls are affected by the moon, they are unable to stop the curious Charlotte...

Cleo decides to restart her friendship with Lewis and embrace her abilities, while Emma is shocked with the new supervisor who has big changes planned.

Zane learns of the myth of Ambergris, a fragrance that can make mermaids fall for any man that wears it. When he buys it, Nate ends up wearing it and Emma, Cleo and Rikki all fall for him!

Lewis is puzzled when he dreams about Cleo being photographed by people. Later, he and Cleo take Eliot and Kim to the marine park. Meanwhile, Emma thinks something is up between Ash and Rikki.

It's full moon and the girls insist that they don't need Lewis to assit his help as all three girls are staying at Emma's and Ash is coming over. When Cleo and Rikki fall under the moon spell, can Lewis stop them from revealing their secret to Ash?

For the first anniversary of the girls being mermaids, Cleo decides to throw a party. However, Emma and Rikki fall out following a fight between Ash and Zane and Cleo may have to celebrate alone.

Lewis is trying to find more information on the moon pool and stumbles across research on it by Max Hamilton from fifty years ago. Will Lewis reveal the girls secret to him in order to complete the puzzle?

Charlotte demands answers to why Lewis is hanging out with the girls so much. She starts to believe an excuse from Cleo, but then a discovery from inside Max's research brings her to the secret! Meanwhile, Ash decides to help Emma with her "fear of water"

Charlotte's stubborn nature and thirst for knowledge leads her to Max, who confirms her suspicions and leads her to the Moon Pool. Lewis meanwhile is having trouble trying to keep their relationship together.

The girls decide that they should accept Charlotte, and the four work together when they need to join the volleyball team to avoid failing Physical Education.

Charlotte is determined to prove her love for Lewis and show she is better than the other three, and refuses their advice and takes matters into er own hands when Nate causes trouble for Lewis.

More friction arises, this time over Lewis' birthday party. Charlotte takes control and drives Rikki away from the party. However, things go out of hand and it is up to her to save the day.

Angry over the short friendship with the girls, Charlotte forces Lewis to choose between her and his friends. This results in Cleo to feel isolated and she runs away and gets lost. When he is informed, Lewis must make up his mind: Cleo or Charlotte?

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.

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.

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.

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.

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

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.

Cleo's family and Sam go on a picnic to the beach, which leads to tension when Cleo refuses to go near the water. Kim abuses the fact that her father is happy in order to get lots of gifts. Will's sister Sophie competes with Bella to get the job Bella wanted at Rikki's Cafe.

During a full moon, the girls stay at Cleo's and Bella is attacked by the water creature. At the same time, Will decides to return to the moon pool after making the connection between his previous encounter with the moon pool waterfall and the timing of the full moon.

Cleo starts to experiment on the moon pool water without Lewis' knowledge, but things start going wrong when Cleo's fish Hector gets trapped in the bubble of floating water. Meanwhile, Lewis has to play golf with Cleo's father.

After Bella gives Will a shell-like fossil she found while swimming, Will becomes suspicious as the fossil is of a rare kind. Rikki realises how close Will is to finding out their mermaid secret and warns Bella to stay away from Will.

Bella helps Will with his free-diving training but when she realises he's more interested in her as a mermaid than a girl, she's hurt. Rikki and Cleo have to improvise when the cafe's first corporate function is actually a children‟s party.

Rikki receives counterfeit money at the cafe and is held captive by criminals on a boat. Bella and Cleo are forced to reveal the trio's secret to Will so they can rescue Rikki together.

Kim attempts to derail Don and Samantha's wedding. Lewis receives an opportunity to study in America. Cleo realises she's got to let Lewis live his own life and let him go overseas.

Will pushes himself too far when Zane challenges him to prove his skills as a free- diver. The girls discover a unique crystal in the rock from the Moon Pool.

Sophie uses Bella's idea for a fundraising concert and presents it as her own to Rikki to gain publicity for the cafe. Cleo's caught in the crossfire with Kim when Samantha moves in and puts her stamp on the Sertori home.

Rikki's frustrated by the water attacks and goes to Mako Island on a full moon to confront the strange force in the Moon Pool. With Cleo and Bella delayed, Will pursues her and discovers she's been affected by the experience.

Cleo's introduced to Ryan, a young geophysicist who's working for Samantha. Rikki doesn't react well to Cleo consulting Ryan about the Mako rock and a fracture begins to appear in the trio.

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.

Will competes in the Free-Diving Championships but afterward chooses to break from the sport and shrug off Sophie's influence on his life. Rikki sees Sophie kissing Zane at the event and breaks off their relationship.

Zane installs Sophie as head of staff at the cafe. Bella develops a sneezing allergy that also accidentally triggers her powers. Sophie seizes on the problem and looks to fire Bella and the band.

The girls discover the Mako crystals contain immense energy and need to mount a rescue mission when Zane jealously steals one in an effort to gain Rikki‟s attention.

The girls sit their final school exams and have to avoid a water attack in public when the full moon rises early. They confront the water force in the Moon Pool and are given a message about Mako Island.

Bella's eager to ask Will to the end of year party until she sees him asking Rikki. A big misunderstanding occurs which prompts Will to express his true feelings for Bella. Sophie tries to get Zane to change the name of the cafe.

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.

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.