Extend the swimming season with a 28 x 14 ft solar blanket that absorbs sunlight by day and limits heat loss at night. A 16 mil Pe film with closed bubble design lifts water temperature 8 to 15 C and cuts evaporation by up to 95 percent. The cover trims debris intake so skimmers run less and leaves stay out of the basket. The blanket can be trimmed to match irregular shapes making it compatible with inground and above ground rectangles or free form pools maintained at Cl below 2.