On Silver Tides

Kelda has always protected her little sister Isla from danger on the rivers, and from the suspicions of their community. For Isla cannot breathe underwater – and so her very existence is forbidden by silvermen's Lore. Now the rivers of England are growing sick: monstrous creatures are awakening and a fierce torrent of blame falls upon Kelda's family. When betrayal comes, the sisters escape on a desperate journey upstream. Joining forces with a mysterious boy, Kelda discovers the darkest depths of her kind's secret history.

Dylan was born with two spirits: human and monster. When he and his family dive underwater, they become wyrms, enormous guardians of the seas. Yet Dylan hates his second spirit, and fears he will hurt innocent people. With his family away on a mission to quell a rising danger in the ocean, Dylan takes his chance to change himself for good and feeds his second self to a spirit eater. But things go awry, and Dylan is left half-changed, with the creature ever on his tail.