This was also part of the Survival Swimming course that used to be mandatory at Georgia Tech back in the olden days. At some point in the class, we had to jump off the high dive, use our pants as described, and remain floating in the deep end of the pool for some length of time (30 minutes I think?)

Fun class, but I shouldn't have taken it in a poorly insulated gym at 8 am Winter Quarter. Brrr.