Drowned in Demand — Gaja J. Kos

Drowned in Demand, the first book in the Drowned novella mini-series.

Dawn is a Rusalka. But not quite. During her fifty-year imprisonment in the humid morass the water nymphs call home, she had managed to hold on to some of her humanity. 

Aelius is the person who had tethered her back to the world she had once known. A ruthless businessman, eager to dispatch his competitors. Permanently. 
 
A water nymph's sexuality is a weapon. But when it comes to her employer, Dawn is the one left defenseless, submerged in unfathomable attraction for the mysterious man.