Risky Business by Nora Roberts

Cozumel had been home to Liz Palmer for ten years. She was settled, respected. Her Black Coral Dive Shop was the best on the island. She no longer missed Houston, or thought about the man who didn’t want her or their child. And for two short weeks, Cozumel was home to Jerry Sharpe, the diving instructor she’d hired. Until they found him–murdered. Suddenly Jonas Sharpe, Jerry’s twin brother, stormed into her well ordered life with grief in his eyes and revenge in his heart. He plunged them both into the desperate world of drug smugglers–and into the dangerous depths of passion.