Riverkeep — Martin J. Stewart

The Danék is a wild, treacherous river, and Wull Fobisher's family has tended it for generations -- clearing it of ice and weed, making sure boats can get through, and fishing corpses from its bleak depths. While recovering a drowned man, Wull's father -- the current Riverkeep -- is pulled under. When he emerges, he is no longer himself: A dark spirit possesses him. In an instant, Wull is Riverkeep, and he must care for his half-father.

When Wull hears that a cure for his father lurks in the belly of a great sea-dwelling beast known as the mormorach, he embarks on an epic journey down the river. Along the way, he faces death in any number of ways, meets people and creatures touched by magic and madness and alchemy, and finds courage he never knew he possessed.