Red Tide

From the New York Times–bestselling author of the Dexter novels: "A game of cat and mouse that builds to an utterly terrifying climax on the high seas" (Publishers Weekly, starred review).
Ex–cop Billy Knight wants to ride out Key West's slow season with the occasional fishing charter and the frequent beer. But when he discovers a dead body floating in the gulf, Billy gets drawn into a deadly plot of dark superstition and profound evil.
Along with his gun–happy friend Nicky, and Anna, a resilient and mysterious survivor of her own horrors, Billy sets out to right the wrongs the police won't-putting himself in mortal peril along the way.