If we're talking tropical, I love love love the Cayman Islands. They're hot, beautiful, and wonderful for swimming, snorkeling, and all kinds of exploring! I swam with Sting Rays when I was there a few years ago and it was one of the most incredible experiences of my life. St Thomas is also in the Virgin Islands and is very lovely as well. The water around these islands is the most beautiful blue I've ever seen, it's incredible.