The Lure of Shapinsay by Krista Holle

Blurb:

Ever since Kait Swanney could remember, the old crones of the village have been warning her to stay away from the selkies. They claim that like sirens of old, the seal men creep from the inky waters, shed their skins, and entice women to their deaths beneath the North Sea. But avoiding an encounter becomes impossible when Kait is spotted at the water's edge, moments after the murder of a half-selkie infant.

Kait is awoken unexpectedly by a...