We are from Texas and have our own pool we do not even get in it until the water temp is above 84 and the outside temp is greater than 90..You raise a good point. How cold is too cold? Just depends on the individual. The record cold water temperature at Castaway Cay is 73 degrees. Is that too cold? My gym keeps it's outdoor pool at 70 degrees in the winter, and I swim year round, so for me, the water at Castaway Cay will always be warm enough for me to swim. Now, we were there on January 2, and the air temperature was 75 and the water 74, so it felt cool when you were wet getting out of the water. But the water was nice and warm.