Sea Change by Robert B. Parker

When a woman's partially decomposed body washes ashore in Paradise, Massachusetts, police chief Jesse Stone is forced into a case far more difficult than it initially appears. Identifying the woman is just the first step in what proves to be an emotionally charged investigation. Florence Horvath was an attractive, recently divorced heiress from Florida; she also had a penchant for steamy sex and was an enthusiastic participant in a video depicting the same. Somehow the combination of her past and present got her killed, but no one is talking-not the crew of the Lady Jane, the Fort Lauderdale yacht moored in Paradise Harbor; not her very blond, very tan twin sisters, Corliss and Claudia; and not her curiously affectless parents, living out a sterile retirement in a Miami high rise. But someone-Jesse-has to speak for the dead, even if it puts him in harm's way.