The frilled shark has often been termed a “living fossil” it rarely grows longer than about 6.5 feet (2 meters) and almost never visits the surface. It has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of the gill slits.
The International Union for Conservation of Nature (IUCN) has assessed it as Near Threatened, because of its very low reproductive rate even incidental catches may deplete its population. This shark, or possibly a giant relative, has been suggested as a possible source for reports of sea serpents.