Indefinitely Wild has a fascinating look into the “Rewarming Drill”, performed by Navy SEALs to prepare for extreme cold weather survival:
The troops would drop their packs on the shore and march ahead fully clothed until they were neck deep in frigid water. For 12 minutes they shivered until John gave the order. With their clothes sopping, violently shaking, they emerged from the cold lake into colder air.
It’s absolutely incredible how they recover from their swim, and a true testament to the value of having the best equipment in the worst conditions:
“With a great clothing system there’s no need to carry extra layers,” John says. “It should be able to perform as a symbiotic system in the most uncompromising situations.