In the female empowering world of Terrene, a world very much like our own, but where young girls can have real power, a new story has arisen.

Set on the beautiful Queensland coast in northeast Australia, four thirteen-year-old girls - and a boy this time - are all riders of the waves: they each have the power to call up a seahorse drawn from the crystal blue waters of the Coral Sea.

But a life on the ocean waves leaves them all at sea when Petra Kerr, the Oil Baroness, starts pumping illegal oil in the area, threatening the precious ecosystem.

It's up to twins Melbourne and Sydney Fisher, Indonesian cousin Memberi Bambang, and friends Adelaide Brewer and native Australian Darwin Tonkin, to find a way to stop her. Their safe plan seems to be working - until Petra Kerr learns who they are, and decides to stop them before they can stop her.

Like its predecessor Cloud Fighters, this is a top-of-the-line story aimed at middle-graders and young teens.