“Dutch East Indies (in the days before the introduction of man-made fillers, “kapok”, a tropical plant fiber was an important padding in such items as life jackets and mattresses). When the islands fell to the Japanese, our kapok supply was cut off . . . and some form of replacement had to be found immediately.
It was then that a Chicago company began to substitute cattail cotton in furniture cushions and baseballs. Soon afterward, the Navy decided to look into the possibility of using the fuzzy heads of the aquatic weed in life belts and aviation jackets. A wartime water-resistance test demonstrated that-even after 100 hours of submersion-the “swamp down” was capable of maintaining buoyancy. So, cattail fluff, (along with milkweed down), was briefly seen as a “war effort resource”. (source)