Ralph Pace / Swell Shark (Cephaloscyllium ventriosum) egg case and embryo, Monterey, California

Alex Mustard / Draughtsboard Shark / Australian Swellshark (Cephaloscyllium laticeps) swims through a giant kelp forest (Macrocystis pyrifera). Like a pufferfish, this species of shark is able to rapidly swell with...

Juergen Freund / Eggcase of Swell shark showing embryo. (C. ventriosum) Pacific Cephaloscyllium

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) egg case with embryo, sometimes called mermaid's purses, the pups will hatch in 7-10 months, native to the Pacific Ocean

Norbert Wu / Swell Shark (Cephaloscyllium ventriosum) swells up as defense, California

Norbert Wu / Swell Shark (Cephaloscyllium ventriosum) underwater, so named because it swells up as defense against predators, California

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) eye

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) close-up of teeth

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) close-up of face

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) pair

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) egg cases with embryos, sometimes called mermaid's purses, the pups will hatch in 7-10 months

Flip Nicklin / Swell Shark (Cephaloscyllium ventriosum) egg cases with embryos, sometimes called mermaid's purses, the pups will hatch in 7-10 months