Cayman
Definitely the Westin in Grand Cayman. It has the best beach. Small reef offshore. Better reef about a mile+ down the beach slightly past the Marriott. (It's off of the Sunset Cove resort, but you have to go in near the Marriott and swim a couple hundred yards to get there). You can also take a jitney down to Cemetery Beach, and snorkel Cemetery Reef (a couple hundred yards offshore). There are other locations as well, but those are the main ones if you are staying at the Westin (or the Marriott or the Ritz).