Swell shark
When threatened, this shark swallows sea water, puffing up to twice its normal size. A bigger, bloated shark is hard to pull from its home.
Some sharks have to keep moving to breathe, but swell sharks can pump water over their gills to breathe. This allows them to snooze quietly on the sea bottom or wait in ambush for prey without moving.
No bones about it
Sharks don't have bones like you and me. Instead they have cartilage—the same kind of material we have in our ears. Cartilage is lighter than bone, which helps keep sharks from sinking. Sharks also have large, oily livers that help them float when they swim.
Enter at your own risk
To catch dinner, a swell shark simply lies on the ocean floor with its mouth open wide. As fishes or crustaceans pass by, the shark sucks them up. Sometimes, the shark just lies still, letting its prey wander into its mouth or get swept in by ocean currents.
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