Quite a few people have written in to tell me about this Australian television show. It's about three regular teenaged girls named Cleo, Emma and Rikki who are given the power to be mermaids. The series revolves around these three girls coming to terms with their newfound abilities, and the wacky hijinks that ensue as they avoid being found out. The three girls also have their own individual powers: Cleo can manipulate water into shapes, Emma can freeze water and Rikki can boil water. At least, that's what happens in the first season... I have yet to watch the second one, but I've read that there's a fourth mermaid who joins them, and all of them get a power up. There's a third season on the way, too.
This show has a few similarities with another Australian production (Mermaids) in that the light-hearted tone is about the same, and there are three mermaids who each have their own individual powers, but the mermaids in H2O: Just Add Water are all humans who are given the ability to become mermaids. That, and the stories are pretty much centred around teenage-type adventures that appeal to teens and young girls. An interesting aspect to this show is showing how the girls have to cope with their powers both giving them advantages and (even more distinct) disadvantages in what they can or cannot do.