Two things are not fun when swimming:. Cold feet and feeling like you're fighting to kick your feet. Our Thermal Swim Socks aim to lessen both of those issues by using a thin, 2mm Yamamoto Super Stretch Neoprene with our Zirconium liner in the foot area. Thinner neoprene is less buoyant, meaning easier and more natural kicking than a thicker neoprene sock or bootie. The Thermal lining maximizes warmth to help keep your feet cozy. Typically worn under your wetsuit, we increased the length of the sock to reduce water entry. The textured bottom helps prevent injury to feet when walking or running on rocky surfaces. They come in handy on long transition runs too. Available in 2 sizes.