You Can't Kill a Dead Man — Daniel Panger

The suspicious death of a friend investigating a Mexican drug-smuggling operation prompts Los Angeles doctor David Gordon to follow in his footsteps in an attempt to discover the true cause of his friend's death. His investigation leads him to a luxurious Mexican resort where at poolside the bodies are beautiful and no one gets wet. But that's not all he finds. He soon discovers that You Can't Kill a Dead Man.