About h2o just add water
H2o just add water is about four mermaids and their lives. In the first season, three girls, Cleo Sertori, Emma Gilbert, and Rikki Chadwick, find the moonpool in the volcano on Mako Island. They go into the pool while a full moon is over the vent of the volcano. The magic there turns them into mermaids when they touch water. They also get cool powers, such as moving water (Cleo), freezing water (Emma), and heating water (Rikki).
In season two, there is a girl named Charlotte that likes Lewis, although Cleo is his girlfriend. Charlotte then discovers the moon pool and jumps in it during a full moon. She turns into a mermaid. Charlotte then causes trouble for the girls, since she has all of their powers combined. Cleo also gets new wind powers, Emma could freeze a room, and Rikki makes lightning. At the end, they are able to get Charlotte in the moonpool under when the planets are lined up and take her mermaid powers away.
In season three, thankfully, Charlotte is gone, and Emma goes on a world tour with her family. Another mermaid pops up, Bella Hartley. She has been a mermaid since she was nine, so she's good at protecting her secret. In season three, there is a water monster that try's to bring the mermaids to the moon pool to watch a comet coming to earth. When the mermaids find this out, the use their powers to deflect the comet from coming to earth.