Kim Sertori


Portrayed by:
11-12 (Season 1)
12-13 (Season 2)
13-14 (Season 3)
First Appearance:
Last Appearance:
Donald Sertori (Father)
Bev Sertori (Mother)
Samantha Roberts-Sertori (Step - Mother)
Cleo Sertori (Older Sister)
Angela (Cousin)

Kim Sertori is Cleo's annoying little sister who is always snooping around Cleo's room and is also always leaning against Cleo's door with a glass and hearing everything she says. She was close to discovering the girls' mermaid secret once in the first season. That is when Kim finds Cleo's Diary in which she has written all things to do with mermaids. When Kim finds this out, she tries to expose Cleo, Emma and Rikki as mermaids at the Miss Sea Queen pageant in the Sea World Marine Park. Kim also believes that Miriam is their Mermaid leader, and another follower is Miriam's friend Tiffany. Cleo, who is on the stage dressed as a jellyfish, protects herself with her power while the other girls' costumes are ruined. Then, Cleo tells Kim the diary was a homework assignment about "The Little Mermaid" and the tail was a costume. During season three, Kim is more spoiled and bratty than in the previous two seasons because she thinks she can do whatever she wants and can be the girl who has more than one boyfriend. She even has a pink, sparkly, jeweled cellphone. Kim hates Sam, even when she gets married with Don by stealing the rings and turning on the sprinklers at their wedding, which later Cleo fixes her dad's wedding by making it a Mako Island only smaller. That episode also shows Lewis departing to America to a school of science. That's when later Kim changes her mind about Sam, and the marriage.


At the beginning of the series, Kim has wispy-looking bangs and generally chooses to plait her hair. She often ties the braids with wide bands that match her outfits. She seemed to be girly, often wearing pink or purple garments. She seems to share her sister's taste in clothing, as she often "borrows" Cleo's outfits. She has a round, freckled face with a bottom nose and eyebrows a shade darker than her honey blonde hair. Throughout the series, Kim physically (though not mentally) matures quite a bit. She grows taller, and her body starts to show signs of womanhood. Her hair seems to darken a few shades, and she grows out her hair, choosing to wear it long and loose, sans fringe. Her taste in clothing also evolves, as she begins to prefer shorter skirts and more stylish tanktops over her previous preferences.


Kim's role is the series is a minor villain, one intended to serve as a source of constant conflict and friction, in both the girls' home life and their mermaid life. She is incredibly nosy and likes to snoop on her sister. Her favorite pastime seems to be vexing her elder sister, and she always is coming up with new schemes