Contraband by Stuart Woods

The story starts with a small plane crashing near lawyer Stone Barrington's yacht off the Florida Keys. When Stone goes to rescue the pilot, he sees several metal cases on the plane but doesn't have time to explore. The next morning, the cases are gone and the pilot is claiming amnesia. When Stone and his friend Dino (top cop in NYC) head back to the Big Apple, they get involved in a double murder--which turns out to be possibly related to the plane crash in Florida. Of course, Stone sleeps with every woman who crosses his path, which is getting a little ridiculous. But the basic story was interesting. Good beach book.