Salt Away — Aaron Galvin

Marisa Bourgeois warned Kellen that the Salt tides are ever moving, ever changing, their melody dark and deep. There is no escape for the poor souls drowning in their wake, and he is one of those unfortunates caught in its deadly sway.

Kellen doesn't believe in ridiculous prophecies though.

A Selkie slave, forced to fight for his life and the enjoyment of others, he has faith in himself and his ability to overcome any obstacle. He'll do anything to regain his freedom, murder included. What Kellen doesn't know is some prophecies are real. That an ancient and nameless voice, long Salting away in secret, might indeed be singing of his fate...and it doesn't care what Kellen believes.