Heavy people do not need a higher buoyancy PFD because of their weight. Hypothermia - A lowering of body temperature, which can endanger survival. Water transfers heat away from the human body 25 times faster than air, so even moderate water temperatures can be dangerous in a relatively short time. Inherently Buoyant - A device which relies on buoyant material for flotation. Plastic Foams - Materials consisting of closed plastic cells which trap air and provide flotation.
Rigid foams used in ring lifebuoys are often polyurethane.
A one pound force equals about 4.4 Newtons.