Diamond Reef by Douglas Pratt

Chase Gordon has the life.
The former Marine works part-time as a bartender to support his life island-hopping on his 40-foot sailboat. When the pretty young wife of one of his fellow Marines shows up looking for her husband, Chase steps in to help her out.
Immediately, he finds himself in a stand-off between one of South Florida's most dangerous drug dealers and the D.E.A. Now, he's left wondering what kind of trouble his friend might be facing.
Can Chase even save his fellow soldier?
Filled with action and adventure, Chase Gordon is the next Travis McGee.