The Grotto pool at the S/D is definately heated. We were there this year over New Year's, and the water was warm, but the air was frigid. I don't know if the weather this January was typical or not, but it was extremely cold and windy at night, and the days could be pretty chilly as well. I can swim in almost any weather, but DW and I only managed to enjoy the hot tubs this year, and even then, the wind took us back to the room fairly quickly. By contrast, two years ago we went to the Poly over MLK; the weather was great for swimming, and the Poly pool was also heated to make it very comfortable (though we missed the hot tub!)