16 ft. x 30 ft. Oval Solstice Solar Blanket Swimming Pool Cover - Blue. Reduces evaporation saving water and costly chemicals. Extends swimming season by up to 6 weeks. Solar blankets are made from a durable polymer material with thousands of tiny sealed air bubbles. They float in. bubble side down in. on the surface of your pool water when the pool is not in use and allow solar energy to pass through which is then trapped as retained heat in the pool.