What can a swell shark do?

The swell shark (Cephaloscyllium ventriosum) is a catshark in the family "Scyliorhinidae". It is found in the subtropical eastern Pacific Ocean between central California and to southern Mexico, with an additional population off the coast of Chile. As a defense, the swell shark is able to expand to approximately double its regular size by swallowing water.

When the shark feels threatened, it will bend its body into a U–shape, grab its tail fin with its mouth, and suck in water. Doing so causes the shark to enlarge in diameter and makes it much harder for predators to bite or dislodge. The swell shark is capable of swelling by using water or air, which is stored in the stomach until released. When letting air out, the swell shark makes a dog-like bark. Swell sharks are non-aggressive and are considered harmless to humans.