Right now my choice would be Bonaire. Yeah I know, where is Bonaire. Well, it's an island 50 miles off the coast of Venezuela. Right between Aruba and Curacao.
Why? Because I scuba dive, too. As I age I'm getting a little less tolerant of temperature changes. Temps run about 75 in the winter and 88 in the summer. Right now it's been about 83 during the day and 80 at night.
For diving the water temp ranges from 78 in the winter to about 84 in the summer.
22 incjes of rain per year. It's out of the hurricane belt so hardly ever has any bad weather. Water vizibility averages about 80-100'. Don't need a boat to dive. It's the shore diving capitol of the world.
Crime is zilch. People are friendly and almost all speak English. And the island always seems to attract a ton of tall, slim, blonde girls from the Netherlands. Yummy.