Amy is the main character of the series, the first of the mermaids and their leader. She quickly makes friends with Brenna and was already friends with Kelsey before transforming after being trapped in a cave by a thunderstorm. She has the power to control water and used to own all three powers (due to there not being enough elements).Her tail changes from pink to blue in season 2 episode 4~Blue Moon.Then, in season 3 episode 6~Answers Found Blaire comes to Amy's house and finds Amy and Kelsey sleeping with tons of candy.Then Kelsey tests out the ingredients Blaire found in her mom's old stuff then has Amy to drink it.Then when Amy drinks it she pops her tail, Blaire, Kelsey, and Amy also realize Amy's tail changes from blue to indigo and smells like cupcakes.She is the younger sister of Tess Samuels.
Brenna is the new girl in season 1.She quickly befriends Amy,but becomes suspicious of her. She accidentally sees her tail in a picture, and wants Amy to help her find the "fish." Brenna swims into the cave while pursuing Amy, and becomes a mermaid with a rainbow colored tail (which turns yellow in Season 3). Her friendship with Kelsey had a rocky start at first, but eventually Kelsey accepted her. She has the power of fire, loves to eat, and is friends with Bill the Ball.
Kelsey is friends with Amy and used to resent Brenna, but they eventually became friends. She became jealous when she wasn't invited to a party and snuck in, where she saw Amy pop a tail. After confronting her and Brenna, she was let in on the secret. She made them a scrapbook with pictures of them as mermaids, but got mad when Amy blamed her for it falling into the ocean, and nearly drowns herself trying to find it. She is transformed into a mermaid, with a light green tail and the element of ice. She has a huge love for science and is the brains of the group.
Blaire met the girls in Season 3, after seeing them swimming in mermaid form. She revealed that her Mom and Grandmother was a mermaid, and her Dad took up fishing so he could find her.She also revealed that she wasn't a mermaid because it skips a generation. It is unknown if she will become a mermaid, although she is able to breathe underwater (fortunate considering the fact that she cannot swim). Amy, Brenna, and Kelsey doesn't know that Blaire could possibly be a siren.