It's a full moon and the three mermaids Nixie, Lyla and Sirena are tasked to guard Mako and the moon pool. While Zac and Cam go camping on Mako island. When Zac falls into the moon pool they don't know what to do and leave him on the beach. The next day Zac finds out what he is and what he can do so he tells Cam. Because the girls let the land boy as they call him in the moon pool they are being cast out by their pod. So they decide to fix the problem. Written by Victoria Petrova

Sirena, Lyla and Nixie must turn Zac back into a land boy. Using Sirena's Moon Ring, they give themselves legs and walk on land to begin their task.

Attempting to capture Zac in his natural environment, Sirena, Lyla, and Nixie follow him to school. When their plan fails, the school principal, Rita Santos confronts them and confiscates Sirena's Moon Ring. In trying to get the Moon Ring back, the mermaids uncover Rita's secret - she too is a mermaid! Begrudgingly, Rita agrees to help the mermaids while they're on land. Written by Ashley Brooks

Nixie and Sirena won't help Lyla try to zap Zac's powers, so Lyla decides to do it alone. This misfires when a waitress spills a drink on Lyla and Lyla rushes to hide in the refrigeration room before she transforms into a mermaid! When she can't dry her tail, Nixie and Sirena must save her before she is discovered! Written by Augusta Knight

Rita tells the girls to go to the Moon Pool while it is raining, where they will be safe. Nixie obeys, but Lyla and Sirena do not. They attempt to use the Moon Ring to stop the rain, but instead make it snow indoors. They develop a rash and Dr. Blakeley, Zac's father is called to take care of them. Written by Ashley Brooks

Joe, David's brother has bought a new boat and decides to take it out for a spin. His fish finder locates a dolphin, but that dolphin is actually Nixie.

Believing that Zac's unusual behavior is a result of feeling lonely, Evie decides to throw Zac a surprise pool party, against both Cam and Zac's wishes. Because of his being a merman, Zac isolates himself from the party when Lyla tries to console him. After seeing the two together, Evie believes Zac's behavior is the result of him seeing another girl. When Cam hears of this, his frustration with Zac increases and he pushes Zac into the pool, where his secret is exposed to the mermaids. Meanwhile, Evie's friend Carly becomes upset when her crush, David, spends all his time with Sirena. Written by Ashley Brooks

The first full moon since Zac was transformed into a merman has arrived and the girls believe that complete isolation from the moon will rob Zac of his powers. Despite the attempt, the full moon overpowers Zac and he is exposed to moonlight, drawing him to the Moon Pool. The girls desperately follow Zac to prevent him from finding the Pool. Written by Ashley Brooks

Lyla convinces Sirena to use her beautiful singing voice to enchant Zac to follow their orders and remove his powers. This backfires, however, when her voice enchants David and he focuses his attention on Nixie, to Sirena's disappointment. Sirena and Lyla enlist the help of Rita to find a cure. Meanwhile, when Evie begins to worry about the big exam, Zac uses his powers to sneak into Rita's office and find the test answers, not knowing this would upset Evie. Written by Ashley Brooks

Zac wants to know exactly how he became a merman, so he decides to return to Mako to find out the truth. However, the girls know that Zac doesn't know about the underwater entrance or the fact that the land entrance does not open unless the full moon is out. When Sirena and Nixie strictly reject Lyla's request to use Sirena's Moon Ring to open the entrance, Lyla steals Rita's Moon Ring and goes to Mako Island with Zac herself. Written by Ashley Brooks

Sirena paints a shell for her sister Aquata and shows it to Lyla and Nixie. Nixie tells her she'll never see her again so she shouldn't bother. A despondent Nixie meets a young boy named Ben and gives him advice which makes him run away. Zac researches tridents online. Cam looks at the computer's history but Rita catches him. Rita tells Lyla and Sirena about the trident and a pod of mermen that rose up out of Mako eons ago that took an army of mermaids from all five oceans to defeat. Written by grrlpunk

Evie learns Zac is researching tridents while doing algebra homework together. Lyla tries to get Nixie and Sirena focused on keeping Zac from finding the trident. Rita won't keep giving the girls money so Nixie makes a deal with Evie to sell Sirena's handcrafted shell bracelets at the Ocean Café. Zac catches a glimpse of the end of Sirena's tail while she's gathering shells. Written by grrlpunk

Rita and the girls worry about the upcoming full moon's effect on Zac. Nixie thinks they should let Zac find the trident so they can take it from him and hide it. Lyla thinks they should come clean with him so he'll in hopes that he'll understand and stay away from it. While Lyla warns Zac to keep away from Mako Island during the full moon, Evie sees them holding hands and breaks up with him. Cam discovers that the girls know Zac's secret but feels uneasy about them helping him. Under the light of the full moon, Zac goes after the trident with the girls close behind. They prevent him from attaining it but he sees them in mermaid form, causing him to become angry. Written by grrlpunk

Lyla is upset that they've lost Zac's trust. Rita confronts Zac on his dropping grades. Rita convinces the girls to restart their training since they never finished mermaid school. Zac and Evie work on reconciling their relationship. Zac and Cam are suspicious that Rita is a mermaid so Zac tests their theory when he and his parents have a meeting with her. Zac threatens to expose Rita because he feels the girls betrayed him. The girls decide that if Rita can't live a normal life, neither can he. Written by grrlpunk

Rita continues to train the girls (this time, how to squeeze lemons from a distance using their fingers). David is holding auditions for a singer to join him in performing at the Ocean Café. Zac gives Evie a glass figurine of two dolphins for their eight month anniversary. Lyla and Nixie see how Sirena and David interact with each other and become concerned that if she gets the singing position, they'll fall further in love and Sirena will leave the pod forever (just like Rita did). Sirena tries out and sounds terrific but Lyla and Nixie interfere using the technique Rita showed them to strain Sirena's vocal chords. Her voice goes so high, it smashes Evie's figurine. Zac witnesses them do it and practices the technique on Cam. When Carly tries out, Zac uses it to make her sound fabulous so David hires her. Evie fills Zac in on David's real reason to audition singers: so he could be with Sirena. The girls see each other's sides and make up. Zac regrets what he did and does not assist ... Written by grrlpunk

Showing off his new smart phone, Cam takes pictures and video of Zac swimming in merman form which makes Zac uneasy. Cam annoys Nixie at the Ocean Café, causing her to send his phone flying. Cam sees David put it in his pocket. Rita tells Lyla that she needs to take her powers and training more seriously. The girls clash with Zac and Cam on how to get a hold of the phone. Lyla and Zac have a telekinetic tug-of-war with the phone while Sirena and David perform at the Café. When David's brother calls him on the phone, everyone realizes he does not have Cam's phone. The girls, Zac, and Cam search the Café after it's closed but to no avail. Cam and Nixie deduce what really happened to the phone. When Carly finds it, they quickly hatch a plan to solve the problem. Written by grrlpunk

Rita continues to train the girls (to control water, whatever form it takes). Zac finds a moon ring stuck in a rock on the ocean floor. He breaks it out and gives it to Evie as a gift. The girls confront Zac about how dangerous the ring could be once it gets hit with moonlight. He agrees to get it back from Evie but not to hand it over to the mermaids. Zac's parents have Rita over for lunch. Zac invites Cam and Evie too with a plan to get the ring back. The girls show up lying that Rita invited them so they can alert Rita to the situation. Zac gets hold of the ring but Lyla and Sirena try to take it from him. Rita walks in on them quarreling, is hit by magic from the moon ring, and becomes unconscious. Can they save Rita and get the moon ring from Zac? Written by grrlpunk

The Halloween costume party at the Ocean Café falls on a full moon. Zac and Cam make preparations to go for the trident. Zac tells the girls that he isn't going to Mako Island, he'll be at the party. The girls are suspicious and plan to keep an eye on him all night. Lyla and Nixie cover Carly's waitressing shift for the night while Sirena performs with David and a live band. They keep a close watch on Zac but he makes a dash for Mako and gives the girls the slip. Can they stop him from getting the trident? Written by grrlpunk

The girls must get the trident out of Zac's possession. Meanwhile, Zac and Cam attempt to use it but can't seem to get it to do anything. Lyla keeps trying to warn Zac of it's potential danger and when Evie sees them talking, she becomes suspicious of them again. David informs Evie that they need an article for the school's magazine and Zac suggests interviewing Principal Santos at home. The girls search Zac's house for the trident while he's at school but with no luck. Evie interviews Rita about her background but when the girls arrive, she shifts the focus to them and it becomes more like an interrogation. While David photographs them, Zac snoops about the house and discovers the secret room. He sneaks back in later through the ocean entrance but the girls are waiting for him. Written by grrlpunk

Zac tries to keep the trident hidden from the mermaids. Evie's article on Rita and the girls doesn't go over well, especially with David. Rita warns Zac about the dangers of the trident. Lyla attempts to enlist Evie's help on locating Zac to no avail. Zac practices controlling the trident in the Ocean Cafe and Seafoods warehouse. The girls follow Cam there but get discovered. Rita reveals more secrets about the trident to the girls. Written by grrlpunk

While swimming in the ocean, Zac sees Aquata. She immediately flees to the Moon Pool and is reunited with her sister Sirena. The girls get her up to speed with Zac, the trident, and their ability to walk on land. Zac and Cam discuss the appearance of this new mermaid and interpret it as a sign of reinforcements coming to help the girls take the trident. Aquata informs Sirena that the council has decided that she may return to the pod but Lyla and Nixie still may not. Zac uses the trident to find the Moon Pool. Rita, Lyla, and Nixie convince Sirena to return with Aquata to the pod even though she does not wish to. Lyla and Nixie confront Zac and Cam. Written by grrlpunk

Rita catches the girls looking through her mermaid phials and informs them that they are not ready to learn about them yet. When David goes to deliver Rita's fish order, Evie tags along to snoop through her house. Poseidon steps through a puddle of mixed mermaid phials and sees Evie causing him to transform into a doppelgänger of her. The doppelgänger leaves with David and ends up at the beach with Carly where Cam watches her act bizarrely. Zac pairs up with Lyla to keep an eye on the doppelgänger while Nixie and Sirena try to find an antidote before the real Evie sees her double. Written by grrlpunk

Zac enlists Cam's help in his search for the trident. Rita gives the girls a lesson in camouflage. A worried Lyla goes to check that the trident is still hidden and watches as Zac and Cam find it. She attempts to wrestle it away from Zac but the trident zaps her into unconsciousness. Zac brings her to Rita's house where she, Nixie, and Sirena try to use Moon Rings to heal her but the rings are spent. Zac uses the trident to recharge them so they can save Lyla. Now realizing the extent of the trident's danger, Zac must make a choice. Written by grrlpunk

Cam is angry with Zac for locking the trident back up. Rita invites Zac to come over for training with the girls. Nixie isn't happy when he arrives. She doesn't trust him and is suspicious of his loyalties. Rita and the girls inform Zac of their plan to return him to a normal human but he wishes to remain a merman. As Lyla and Zac grow closer, Nixie becomes more upset, especially since Sirena and David have become close. Cam approaches Nixie about him not wanting Zac to be a merman either. Lyla reveals her wish for Zac to join the pod to Rita, Nixie, and Sirena but they are unsure. Nixie notifies Cam of her interest in teaming up with him to return Zac to normal but can she trust him? Written by grrlpunk

Zac has a nightmare involving the trident and the Moon Pool. Cam apologizes to him and expresses his disappointment in Zac's locking it back up. Zac almost tells Evie his secret. Cam approaches Nixie with a bogus story and a plan for the two of them to put the trident out of Zac's reach. Evie tags along with Cam to Mako Island. Nixie, displeased by Evie's being there, opens the cave with a stolen Moon Ring so Cam and Evie may go in. The two enter the water chamber and Cam takes a hold of the trident. With the Moon Ring losing its power, Cam makes it out, leaving Evie trapped inside and losing air. Carly informs Zac, Lyla, and Sirena that she saw Cam and Evie headed for Mako. Will they make it in time to save Evie and what will become of the trident, now in Cam's hands? Will Evie become a mermaid or will Cam become one? Written by grrlpunk

Cam shows Nixie that he is hiding the trident in his school locker. Evie agrees to keep everyone's secret until after Zac is turned back into a normal human. Cam apologizes to Zac for betraying him. The girls look forward to returning to the pod. Sirena says a tearful goodbye to David. Cam lies to Evie about the mermaids' intentions. Everyone catches on to Cam's scheme and races to Mako Island. Will they succeed in stopping Cam and be allowed to return to the pod? Written by grrlpunk