Shadow — Alice Jamison

Looking for an escape from her lonely existence, Elsa Grey jumps at the chance for a dream vacation on a seven day cruise. Sailing off into crystal blue waters Elsa holds high hopes of finding the man of her dreams, to fill the gap in her life. But, before she can dwell on her loneliness for too long, things aboard her sailing paradise takes a strange and horrific turn. A mysterious creature lurks in the shadows, threatening the lives of everyone on board. Caught up in a fight for her life, Elsa is rescued by handsome, mysterious billionaire Charles Grimm.
Hiding a dark secret of his own, one that makes him well aware of what is wreaking havoc aboard the ship; Charles fights in the shadows to keep everyone safe. Faced with a deadly enemy and his confusing obsession with the woman he rescued, he is in for a difficult battle. Can he keep Elsa safe until the ship docks? Or will his lethal enemy take her from him forever?