we went on 12/21/03 and it was a bit cold, but it was colder than normal for Orlando for a couple of days. We were given wet suits, and there were these heaters all over the place, and so it wasn't too bad, but i would not want to book that again for December as I think we would have enjoyed it more if it hadn't been so cold. The first time I went was in October 2003, and the weather was perfect and you could get by with using a vest.