Sydney Cole came back to Shell Key to disappear.
Driven out of San Diego after a scandal shattered her career, the marine biologist returns to the small Florida town she once called home, hoping to keep her head down and survive what's left of her life. Then the bay starts spitting up warnings: dead fish drifting in a chemical slick, a diver torn apart inside an outflow pipe, and terrified whispers of something massive moving under the water. As panic builds and officials fight to keep the beaches open and the tourists spending, Sydney is dragged into the hunt alongside a disgraced professor and the town's police chief.
What they find is ancient, ruthless, and far more intelligent than anyone is ready for. It is learning the channels, the boats, the people. Every kill brings it closer to shore. And with Shell Key surrounded by water and running out of time, Sydney may be the only one who sees the truth clearly enough to stop it before the whole town becomes a feeding ground.