Amy SamuelsThe main character and The Hero of the series. Amy was the first to become a mermaid thus she takes it upon herself as The Leader of the group. She also has a Sibling Rivalry with her older sister, Tess. She is portrayed by Christine Davis.
Brenna EdwardsAmy's best friend and the Na´ve Newcomer of Season 1. She is a Big Eater and has the ability of heating and boiling things.
Kelsey CorkThe Smart One of the group, Kelsey is the typical Hollywood Nerd. Appearing as a Jerkass to a Jerk with a Heart of Gold in Season 2 as a recurring character, and was a main character in the later seasons. She is portrayed by Emma Dunne.
Blaire HarrisThe Half-Human Hybrid daughter of human Steven Harris and mermaid Terra, Blaire is often used as a source of information for the girls, who are desperately looking for information on there mer-genetic half. On May 11th, her 1st birthday, Terra left her and her dad because of not being able to survive on land, physically and mentally scarring them forever. In Season 4, she is revealed to have the ability to breathe underwater and eventually leaves her friends to live with her mom in the ocean, although she still communicates with the girls every now and then. She is portrayed by Tessa.