Depends on where you are from. If you are from Florida, you likely have stopped swimming in October. Those from further north brave the 40's ad 50's to take a dip in the pool in sunny Florida. Sometimes the water parks close if the temps get lower than about 60 degrees. I have seen some poor life guards on their chairs at the pools in 40 some degree weather... no thanks!
All of the pools are heated to about 82 degrees, so as long as you are submerged, you would be ok... it is just the "getting out" part that may be rough. Early December daytime temps are around 72 degrees.. the later in the month it gets, the further down the mercury could drop, though. Take a suit anyway, in case you get one of those unseasonal warm sunny days.