Which shark inflates its stomach to appear larger when threatened?

The swell shark inflates its stomach to appear larger when threatened. It bends its body into a U-shape, grabs its tail with its mouth, and gulps water into its expandable stomach.

This defensive maneuver can make the shark nearly twice as large and much harder for a predator to bite, swallow, or pull from a rocky crevice. If it is out of water or brought to the surface, it can also take in air. Once the danger passes, the shark releases the contents; expelling air can produce a distinctive bark-like sound.

The swell shark is a sluggish catshark of the eastern Pacific, where it hides by day among algae-covered rocks and hunts at night. It is not the same animal as a pufferfish, although both inflate as a defense. The shark’s common name refers specifically to its ability to enlarge its body by filling its stomach with water or air.