Lewis: "Cleo, everybody is scared of something. But you, you're amazing, you can do anything." Cleo: "Just because I've got these powers doesn't mean I'm amazing." Lewis: I didn't mean the powers."-episode Catch of the Day Cleo Sertori is one of the main characters who became a mermaid in the Australian television series, H2O: Just Add Water. Along with Emma Gilbert and Rikki Chadwick, Cleo discovered her powers after her trip to Mako Island. She was portrayed by actress Phoebe Tonkin in live-ac