Cleo Sertori (played by Phoebe Tonkin) is a protagonist in H2O: Just Add Water.
One of the three teenage girls who transforms into a mermaid after contact with moonlit water on Mako Island. She possesses supernatural water powers, struggles to keep her secret, and navigates romantic relationships with Lewis McCartney. She remains a central figure throughout the series, adapting to her new lifestyle and facing threats like the comet. Emma Gilbert (played by Claire Holt) is a protagonist in H2O: Just Add Water.
One of the original trio of teenage girls who gains mermaid abilities and water manipulation powers after an encounter on Mako Island. She helps her friends manage their secret and adapt to their supernatural lifestyle. In Series three, she departs to travel the world with her family, leaving the remaining duo to face new challenges. Rikki Chadwick (played by Cariba Heine) appears in H2O: Just Add Water.
One of the three teenage girls who transforms into a mermaid and discovers water-based supernatural powers. She works with Cleo and Lewis to maintain their secret while adapting to the challenges of their new abilities. In Series three, she befriends Bella Hartley and joins forces to confront a mysterious water tentacle and an impending comet threat. Byron (played by Christopher Poree) appears in H2O: Just Add Water.
Ash (played by Craig Horner) appears in H2O: Just Add Water.
Nate (played by Jamie Timony) appears in H2O: Just Add Water.
Charlotte (played by Brittany Byrnes) appears in H2O: Just Add Water.
Introduced in Series two as a rival to Cleo, she dates Lewis McCartney after his breakup with Cleo. She gains mermaid powers, becoming the main antagonist with access to all three original mermaids' abilities. Ultimately, she loses both her powers and Lewis, who reconciles with Cleo. Miss Chatham (played by Christine Amor) appears in H2O: Just Add Water.
H2O: Just Add Water (2006) — Character Map & Story Timeline
H2O: Just Add Water (2006) interactive character relationship network and AI-powered story timeline. Explore the connections, alliances, and conflicts between characters across the narrative arc.
AI Narrative Summary
Overall narrative architecture across all 3 seasons, tracking magical evolution, social dynamics, and external threats.
Character Network — 8 Characters
Cleo Sertori (Phoebe Tonkin) — protagonist One of the three teenage girls who transforms into a mermaid after contact with moonlit water on Mako Island. She posses...
Emma Gilbert (Claire Holt) — protagonist One of the original trio of teenage girls who gains mermaid abilities and water manipulation powers after an encounter o...
Rikki Chadwick (Cariba Heine) One of the three teenage girls who transforms into a mermaid and discovers water-based supernatural powers. She works wi...
Byron (Christopher Poree)
Ash (Craig Horner)
Nate (Jamie Timony)
Charlotte (Brittany Byrnes) Introduced in Series two as a rival to Cleo, she dates Lewis McCartney after his breakup with Cleo. She gains mermaid po...
