Well this isn't a real series but a idea that should be a new H2O spinoff.
In the beach town of Rainbow Cove live three sisters name Casey, Tessa, and Flora. On there 16th birthday they went to camp at Mako Island, and during there hike found a mysterious cave were inside is the moon pool. When the full moon shine over them when they enter the pool there lives change forever. The next day they discovered there mermaid tails, and powers that they discover that a beautiful mermaid queen name Amphirite gave birth to three girls born half human half mermaids in the moon pool of Mako Island. While keeping there secret they have to deal with teen issues, and search for there long lost mother.
What do you guys think of it?