We would drive down from Maryland to the Florida Panhandle to visit my parents during our children's Thanksgiving Vacation time.
When we went swimming in the (warm to us) Gulf on one of the Florida Panhandle beaches reserved for the Air Force (permission granted by my brother), some 'official' looking guys drove us and yelled at us, "What do you think you're doing?" We shouted back, "Swimming." They simply shook their heads and drove off and we continued with our beach day. (we were the only people there)
It wasn't until we visited them one August that we realized why those men were worried about us. The water was bathtub Warm! At Thanksgiving time, the water in Florida seemed normal to us because it was the temperature of ocean water off the coast of New Jersey and Maryland during the summer.