Silent Fathoms — Tamara A. Lowery

The search for the third Sister of Power takes Viktor Brandewyne to Mexico and the Devil's daughter. She sends him to find devil's hoof, but doesn't explain exactly what it is. All Viktor knows is that she will use it to try to enslave him once he brings it back to her. His quest strands him in the middle of the shark-infested Indian Ocean with no food or water, no wind . . . and no siren to sing one up for him. Try as he might to reach her, his bond with Belladonna has fallen silent.