air bladder

Noun

 * 1) An internal organ that fish use to control their buoyancy, allowing them to maintain or change depth by changing their density.
 * 2) A type of packing material that consists of an airtight bag full of air, used to cushion fragile items.
 * 1) A type of packing material that consists of an airtight bag full of air, used to cushion fragile items.