Devil Dunes — Mary Sheppard

The sea was restless, and Angie, on her way to Nag's Head aboard the Columbine, was foolish enough to take chances with her safety. As a result, she was washed overboard; and only the action of a tall somewhat frightening stranger saved her life.

But he refused to let his heroism become known and made it crystal clear that to acknowledge having any association with him would be a disastrous mistake on Angie's part if not a fatal one. So she had to go through an elaborate bit of play-acting merely to cover up the details of her perilous odyssey.