H2o: Just Add Water is a TV show about 3 girls who become mermaids if water touches them. They also have powers. They have kept their secret, but they've only told Lewis, Zane and Ash.
Cleo is the peacemaker of the group and has a huge crush on Lewis. She has a younger sister named Kim who's always spying on her. She used to be afraid of water.
Emma is a control freak. She is sensible and confident, and doesn't like change. She's in the 1st and 2nd season, but isn't in the 3rd season.
Rikki is rebellious, sarcastic, and a little self-centered. She was the last to find her power.
Bella is a mermaid who shows up in season 3, replacing Emma. She loves to sing and has been a mermaid since she was very young, unlike Cleo, Emma and Rikki.
Lewis is science freak and is always trying to scientifically find out why they are mermaids. He is Cleo's boyfriend for a while.
Zane is a rich kid who used to be very naughty, but changed his ways after becoming Rikki's boyfriend. He knows about their mermaid secret and will do anything to protect it.
Only seen in season 2, Charlotte is a manipulative girl with a huge crush on Lewis. She will do anything to have him and is always trying to keep Cleo away from him. She becomes a mermaid for a while, but loses her powers at the end of season 2.