H2O: Just Add Water, more commonly referred to as H2O, is an Australian fantasy children and teen drama television show created by Jonathan M. Shiff.

It first screened on Australia's Network Ten and as of 2009 ran in syndication in over 120 countries with a worldwide audience of more than 250 million.

The show revolves around three teenage girls facing everyday teen problems with an added twist: they are mermaids and each has their own unique, supernatural power related to water.

Rikki Chadwick, Emma Gilbert, and Cleo Sertori are three teenage Australian girls who find themselves stranded on the mysterious Mako Island, where they end up in a pool under a dormant volcano just as a full moon passes above them, bathing the pool in light.

Everyday situations, such as bathing and dealing with rainy weather, become tricky as the girls struggle with their newfound abilities, which come with many advantages and disadvantages, while also trying to keep them a secret from everyone else, including their families.

Rikki and Cleo become friends with Bella, but are soon beset by a mysterious tentacle of water with a connection to Mako Island.

The custom costumes took six months to build, with the tails and tops made from body casts and comprising individually hand-crafted scales.

A second soundtrack, featuring music from series three, was first released on iTunes on 17 February 2011,[10] and later worldwide in March 2011.

[11] Several children's books have been released by Nickelodeon UK:[12] H2O: Just Add Water received positive reviews from critics and audiences.

Emily Ashby of Common Sense Media gave the show four stars out of five, saying that it was about "Aussie mermaids send positive messages to tweens.