Secret Water — Marian Perera

To get permission to marry Darok Juell, the man she loves, Yerena Fin Caller undertakes a final assignment for the guild Seawatch. She must investigate two strange occurrences in a fishing village -- the people's refusal to offer food to outsiders, and the disappearance of a scientist who retired there.

She travels to the village with Darok, who's inclined to treat their time there as an early honeymoon. But the villagers avoid the sea, warning Yerena not to eat anything she doesn't find herself. A scrawled word on the wall of the scientist's ruined house leads her to his hidden laboratory, and she discovers something escaped from the laboratory. Something that now waits in the water offshore. Something which nearly defeats her great white shark in their first encounter. With Darok standing between her and the people who want to kill them both, Yerena must enter the ocean -- at night -- to destroy what holds the village in its power.