I think this is an interesting question and it has never crossed my mind to ask something like this before. I used to be a competitive swimmer for 15 years and there were days when I used to swim in outdoor pools with temperatures below freezing and under windy conditions as well as 100+ degrees. I believe water aerobics is a very different type of exercise compared to swimming (especially at the competitive level), so I’m not sure what the correct answer is here. I would say that it depends on various factors such as water temperature, intensity and duration of the workout, age and fitness condition of the participants, to name a few. Living in Florida I would think that outside air temperature is perfect for this type of activity. The only factor to consider is the time of the day the class takes place and the temperature of the water. Below there is a link which I found online that has some interesting information on water temperature (not air). I hope you find this interesting:
I look forward to see what other instructors will post here.