The walrus has a streamlined body that makes it easy to swim and conserve heat. Because walruses have a small surface-to-volume ratio, along with few protruding body parts, they lose little heat in the cold Arctic weather. Meanwhile, walrus forelimbs and hindlimbs are sleek and webbed, like oars. This means walruses can swim up to 35 kph (22 mph) if startled. On land, the walrus uses its hind limbs to get around, but it cannot use them to stand up. Instead, the walrus uses its limbs to thrust its body forward in small lunges while hardly getting off the ground. And walrus blubber, which can be up to 15 cm (6 inches) thick, acts as a cushion when bouncing around the ice and other hard surfaces.