Snorkling/Diving in the Caribbean/Gulf of Mexico

[Lance]

We have decided to take a trip to the Caribbean or Gulf of Mexico this winter. As we have always holidayed on the Pacific side we have little knowledge of the Atlantic. I'm looking for suggestions from those of you who have. I'm going to get my diving certification, and Joan wants to try some snorkling; so we are looking for a destination that can provide both. IE: a shallow reef, (she's afraid of deeper water), where she and I can snorkel together; as well as a good diving area for me. Of course, we also want to partake in the eating, drinking, laying around on the beach, sight seeing, shopping, part of a holiday as well.
We have been researching these areas but personal experiences are always better; so we would be grateful for any of your input.
Thanks, Lance