If 72 degress is cold, then I guess the water has been cold at Castaway Cay because that is the record low water temperature in the region. I'm in California and swimming season starts when the pool hits 68 degrres, so 72 is nice.
We were on Castaway Cay January 2, 2004. The air and water temps were warm, we had sprinkles in the afternoon, and were surprised how many folks headed back to the ship. We were snorkeling, so we were we already wet, and had a nice bike ride in the warm drops.