These socks sit tight to the skin meaning even when water gets down your boots you feet stay dry and warm. Ideal for fishing, sailing, paddling or anything where you don't want your feet cold or your boots wet, simply remove your boots and where these alone. As I did with my sealskinz gloves I filled the socks with water to test there 100% waterproof, and held up 100% no leaks. Excellent piece of kit, would recommend buying your next size up and layering with a normal pair of socks if you are plannign on using them in winter.