So I had my solar heater on all day yesterday, and the water got up to 80. Not quite warm enough for me to enjoy my first dunk, but oh so close (did get in up to my knees). So this morning I went out and checked the water temperature to see where it was...pump not turned on yet, outside temp got to 60 overnight....and the water temp? 80 degrees. Is that possible? or is my floating thermometer wrong?