Cleo Sertori is the oldest child, she has a younger sister who always annoys her. In the very beginning of the second season it says her mother and father split so now she lives with her father.1 and 3 her boyfriend is Lewis McCartney. It's a very hard change when she becomes a mermaid because she can't swim. Her power is to make water do what Cleo wants it to do. Her best friends are Rikki Chadwick and Emma Gilbert for the 1 and 2 seasons, in season 3 it's Rikki Chadwick and Bella Hartley. In seasons 1 and part of 2 and all of 3 her boyfriend is Lewis McCartney.