Along those lines of a floatation device, as a U S Navy Vet, in bootcamp, we were taught that once in the water, you remove your pants, tie the leg openings into knots, and then try to raise the pants over your head ( to trap air ) and then pull them down into the water. Hopefully you have enough air to have a makeshift floatation device. I know this works with most cotton materials that are fairly heavy like jean material. While on a 6 month deployment in the Mediteranian Sea with the America Battle Group back in 1995-96, a US Marine was knocked overboard from the Air Craft Carrier at night, and he used that meathod to stay afloat for over a week before being picked up by Greek Fishermen.