The Thermal Swim Shirt provides warmth to swimmers by trapping body heat with its unique BiPoly fabric. Made from a strong, yet lightweight material, the Thermal Swim Shirt conforms to a swimmer's upper body without restricting range of motion. Used over time, the slight drag effect of the Thermal Swim Shirt will also build endurance and strength. The Nobel Prize-winning Polyolefin fibers provide UVA, UVB and Antibacterial protection, and is chlorine and fade resistant.