I've done a little more research, it looks like the water in Key West averages only in the upper 60's in January. That's too cold for me.

Thanks for the tip regarding limited snorkeling in Curacao. I'd hate to be bored after a few days of snorkeling. A little more variety would be nice. I wonder if taking a day trip to Bonaire is possible.

Doesn't it get a bit stormy around St. John during January?