I have never scuba dived, but I used to go snorkeling in the Gulf when I lived in Florida. As Kellie said, the water is very warm. In the panhandle, the Gulf beaches have white sand, and the water is clear, making for very nice underwater viewing.
I unknowingly swam into the tentacles of a dead Portuguese Man-of-War and got stung across my chest, back, and legs. My brother was fishing on the shore, laughing at me. He said it looked like I was running on the surface of the water, trying to get out of there!