We were there the day after Thanksgiving last year. It was a little chilly that day. I think it was in the 50s that morning if I remember correctly and got up to around 68. The dolphin swims are scheduled all day long. The earlier you check in, the earlier your swim is. I'm not sure if they let you choose later times or not if you check in early. My DH's swim was at 9:30 and mine was 10:30 (or something like that). I kept my wetsuit on all day. The pool (the area without fish) is heated and very warm water. When you get out is the problem. The rest of our trip the days were a little warmer though, so you may have a very warm day!
Sandra