air bladder

noun2

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.

   • The company used to be notorious for excessive packaging, and social media grew littered with examples: three pairs of socks wrapped in puffy air bladders[…] — 2019