The cold weather training of South-Korean army's special warfare force is high level badassery of the level I have never seen before. It's like when nuclear powered attack submarines break the Arctic sheet after surfacing through three feet of ice. But these are humans. Quite literally cool [Republic of Korea Armed Forces]
The one thing I remember from my USMC Cold Weather training rotation was that WET=DEAD! We changed socks frequently because vapor barrier boots made you sweat. We unzipped our parkas is we felt warm, etc. Here these guys are swimming in ice water. Crazy.