Gulps water or air to inflate belly and wedges itself into rocks. When expelling air, it makes a dog-like bark. Rest in caves and crevices, wedges and swells. Ambushes fish or hangs out with mouth agape and waits for an unsuspecting meal. Mollusks and crustaceans, hunts fish and invertebrates at night.
Males have siphon sacs that pump seawater to aid the flow of semen from claspers.
Females lay two greenish-amber eggs at a time. These egg cases are often called mermaid s purses with tendrils that entangle among plants, rocks or coral to keep them in a safe place. These embryos develop in the cases for one year, feeding on yolk, and once they hatch they are instantly ready to eat mollusks and crustaceans. They hatch by using two rows of enlarged dermal denticles along their back which shed shortly after hatching. Swell sharks are members of the catshark family, and are not considered dangerous.