Emma, or Em to her friends, first discovers herself being a mermaid one morning while swimming at the beach. She has the ability to freeze any object or liquid containing water. In the second season, under the power of a full moon aligned with various planets, she develops a much stronger icy power and, with help from Rikki & Cleo, has the power to summon on a hurricane like storm. She liked Byron in the first season. Also, she eventually found love in boy named Ash, who is currently her supervisor at the Juicenet café and was previously a riding instructor who taught Emma's little brother to ride a horse. Emma couldn't stand Ash at first (he was a better horse rider than her), but with prodding from her friends Cleo and Rikki, she realizes her love for him. At the end of season two, she reveals her secret to Ash.
Cleo Sertori
Cleo first finds out herself being a mermaid while taking a bath. She has the power to manipulate the form of water and mould it into a different shape. She can mystically create more water to form a "branch" from a small cup. She can also control wind in series two. She is shy but very bright and a loyal friend. Late in series 1 Cleo and Lewis develop a relationship but he is too clingy so she breaks up with him. A new girl named Charlotte arrives, who is Cleo's friend at first but then Charlotte becomes jealous of Cleo's friendship/relationship with Lewis so Charlotte constantly tries to be with him. Charlotte and Lewis form a relationship, much to Cleo's dismay. Charlotte causes many problems for Cleo in series two, such as stealing her boyfriend, stealing her locket, and even more when Charlotte becomes the fourth mermaid. After Lewis had enough of Charlotte's actions, he breaks up with her and rescues Cleo from sharks. Later in the episode he and Cleo rekindle their relationship.
Rikki Chadwick
Rikki is the new girl in town in series one. She first discovers she is a mermaid when she was hit by water from the park sprinkler system. She was the last to gain her powers. She is able to boil water or anything containing water. In the second season, she develops the ability to start fire and summon lightning. She is a rebellious new girl and a self-confessed loner who finds an attraction in the local bad boy, Zane Bennett. They first fall in love when trapped on a balcony together. They briefly date but find they have too many differences at the end of the first season. Shortly into the second season, they rekindle their relationship, although somewhat casually. She was originally at odds with Miriam, Zane's ex-girlfriend, seen only in the first season.
Lewis McCartney
Lewis has been Cleo's friend since they were five, and following the girls' transformation, he also becomes friends with Rikki and Emma. He is academically gifted, thinks of himself as a scientist and has a passion for fishing.He discovers the girls' secret early on in the series and becomes determined to find the cause. He is in love with Cleo, who reciprocates the feeling and the two form a relationship late in series one. At the beginning of series two, Cleo breaks up with Lewis. They stay friends but remain a little embarrassed. Lewis develops a friendship with Charlotte, the new girl, who has a crush on Lewis and becomes his controlling girlfriend. At the end of series two, Lewis dumps Charlotte because of her behaviour towards the other girls, mostly Cleo. After he saves Cleo from a shark reef, they get back together.
Charlotte Watsford
Charlotte is the new girl in town and is the girls' rival during series two. She enjoys various forms of art and appreciates the sciences. She is friendly at first but becomes jealous of Cleo's relationship with Lewis, so she constantly tries to be with him. After Cleo breaks up with Lewis Charlotte pursues him and eventually the two develop a relationship. She is very selfish, controlling and manipulative and gets paranoid very easily and becomes jealous of Cleo. She is later revealed to be the granddaughter of Gracie, one of the original three mermaids. She becomes the fourth mermaid herself, receiving all three of the powers. After this she becomes very dangerous when angry, especially when Lewis breaks up with her to be with Cleo. The 50 year full moon comes and Charlotte reveals to Lewis that that is how Gracie lost her powers. She plans to strip the other girls powers so that she will be the only special one for Lewis. But after being beaten by the girls, she loses her powers forever, and her friendship with Lewis and all other mermaids.
Zane Bennett
Zane is the local bad boy, and seems to think that he can get away with anything because his dad is rich. He appears to be arrogant, but has been seen to have a softer side. He desperately wants to impress his father, local land developer Harrison Bennett, who is more arrogant. Zane is an excellent swimmer. After becoming trapped on a sinking boat, he is rescued by Emma, and sees the end of her tail before she is able to slip away. Because of this, Zane becomes obsessed with finding the "sea monster". Later on in the first season, to the disappointment of Miriam who assumed that she was with Zane, Rikki and Zane develop feelings for each other after being locked out on a penthouse balcony in a hotel that Harrison Bennett is giving an advertising speech at. While they later break up at the end of the first season because they are "too different" from each other, they rekindle their relationship in the second season after Zane discovers the girls are mermaids. It is found out also that he is very caring.
Ash
Ash is the current supervisor of the Juicenet Cafe (to Emma's disappointment at first, since she wanted the job). Ash is a keen horse rider and has worked as a riding coach. He and Emma have formed a relationship and have gone out on a few dates. In the middle of the second season, in the episode 'Moonstruck', Emma was affected by the full moon \(with Cleo and Rikki) and almost revealed her secret by calling him into the bathroom when she was wet with a tail. Luckily, Lewis steps in and stops him. During the season two finale, Emma reveals that she is a mermaid to Ash, and his only reaction was to smile and say, "Cool" before the end credits roll. Ash also has a falling out with Zane in the Juicenet Cafe, causing the girl's group to split for an episode.
Louise Chatham
Louise Chatham, or Miss. Chatham as she's typically called, is a mysterious elderly woman who Cleo meets while working at the marine park. She hints to Cleo that she knows the girls secret and warns them about the effects of the full moon. Later, an altercation that she has with Zane leads to her boat being declared unseaworthy and Emma invites her to stay at her place. That night, however, Miss Chatham sneaks out at night and sails off with her boat. After an altercation on the boat with Zane, she suffers a heart attack and is taken to a hospital by Lewis. Before going to a retirement residential home, she reveals to the girls that she once was a mermaid too, but that "the burden became too great", so she "had to give it up", hinting that there is a way to give up their powers.
Max K. Hamilton
An elderly man (who is a scientist like Lewis and 50 years ago published studies similar to the ones that Lewis has done), he was a friend and confidant of the original mermaids. His first appearance was in "The Gracie Code" late in the second season when Lewis discovers his old research on Mako Island. Max reveals that he truly loved Gracie, just like Lewis truly loves Cleo, and that he created the three lockets (that the girls wear) for the three original mermaids. He gives Lewis all his old research and pictures of the original mermaids. He declares that Cleo and Lewis are meant for each other, but Lewis ignores them because he was dating Charlotte at the time. Lewis realizes what Max meant when Cleo went missing and Lewis realized how much he cared for her. Max was the one who told Charlotte about mermaids after she declared that she was Gracie's granddaughter. He also revealed that the 50 year moon lines up with all the planets and will possess enough power to take away a mermaid's powers forever with no chance of ever regaining them back.
