The Slapstyx

With the help of the grubby Slapstyx goblins, dastardly detergent manufacturer Zachary Zigstack is turning the oceans into toxic slime infested with ravenous sea monsters.
Twin sisters Georgie and Gem can leave their bodies at will and explore other dimensions – which means they can spy on the Slapstyx and find a way to stop them. But can they do it before all the sea creatures are destroyed? The Slapstyx are dangerous as well as dirty, and have nasty ways of killing people who cross them…