Howard, Amalie. Daring dukes

Series statement from GoodReads.com

Lady Lisbeth Medford, Countess of Waterstone and famed international spy, is caught between the devil and the deep blue sea. On a covert mission, she's determined to infiltrate a notorious smuggling ring in the West Indies as a ship's captain...only her identity has been compromised. Leaving her pursuers in ashes, she boards her vessel to flee, but the men on her heels will stop at nothing until she's paid the piper. The trouble to her front, however, is Raphael Saint, the Duc de Viel, her ship's new aggravating and dangerously charming sailing master who might very well be part of the smuggling ring Lisbeth must bring to justice. But when a new deadly threat on the high seas looms, the only way out of danger might be to face it...together