A Tryst by the Sea. The Siren's Retreat Novellas, #1

Vergilius, Viscount Summerton, has watched his wife of ten years grow more and more distant, and he's determined that this year the marriage will start moving in a better direction. Penelope, Lady Summerton, is also determined that this year will be different. She slips off to a seaside cottage, intending that to be her first step toward a new life free of marital difficulties. Gill ends up at the same seaside inn, where he hopes to plot a wooing no wife can resist. He's determined to reconcile; she's determined to pack his bags, but then the magic of the Siren's Retreat begins to steal over them both.