The Army's flotation bladder assembly could be used as either a canteen or as a personal flotation device for heavily loaded soldiers crossing rivers and streams. The assembly consisted of a 5-quart capacity vinyl film bladder with a nylon cover that featured a funnel neck to aid filling from a still water source and a pocket for water purification tablets.
When being used for flotation purposes, belt loops on the base of the cover allowed the breath-inflated bladder to be attached to the swimmer's trouser belt. Unfortunately by the time the flotation bladders arrived in Vietnam, few troops were employed in the sort of footmobile operations that necessitated the use of such equipment.1
Though the contract to manufacture the assembly was won by Trenton Textiles Eng., the International Latex Corporation fabricated the prototype. ILC exclusively produced the 2-quart collapsible canteens for the military in WWII and the first version used in Vietnam.
1. Jungle Snafus...and Remedies by Cresson H. Kearny (Oregon Institute Of Science And Medicine 1996)