Georgie Codd is scared of fish. Really, really scared. Even on dry land there's no escape: Georgie sees sharks in the dining room, squid tentacles in the street, has nightmares of being stranded at sea.

Granny Codd understands. She has spent her life beside the water, but won't so much as paddle in it. Georgie's boyfriend is supportive, too, even when she decides that the answer to overcoming this fear lies in travelling to Thailand, learning to dive, and swimming with the biggest fish in the world: the massive, mighty whale shark.

Could this immersive therapy actually work? There's only one way to find out. An anxious Georgie quits her job, leaves her life behind, and plunges into a realm of strange creatures, hidden depths, and intrepid diving adventurers. But as her quest expands across the oceans, her shark remains elusive, and everything else starts to fall apart around her.

On this journey that veers towards death and destruction, Georgie must not only track down her shark, but find her way back to the surface.