Dark Tide — William P. Kennedy

TWO COUPLES FIND TERROR IN PARADISE
Bill and Jeanne Chester and Howard and Marilyn Hunter imagined an idyllic week of sun and sailing aboard a luxury yacht in the Caribbean. They were dead wrong.

AND MURDER ON THE OPEN SEA...
Returning from a sumptuous island dinner, they suddenly find themselves captives of the sinister charter boat captain--heading out to sea in the steamy tropical night. At stake are millions of dollars in stolen diamonds and bonds, hidden somewhere on the boat.

BUT THE REAL NIGHTMARE IS ABOUT TO BEGIN...
Struggling to outwit their captor, they finally gain control of the vessel. But soon the powerful lure of instant wealth lets loose an evil madness that turns devoted husband against beloved wife, and loyal friend into mortal enemy. Now, amid the dark, sensuous tides of the Caribbean, four people circle each other in a dance of betrayal, terror and murder.