Well, this may be the one who started all the rumors.
The frilled shark (Chlamydoselachus anguineus) is one of two sharks in the family Chlamydoselachidae, mainly found in the Atlantic and Pacific Oceans, in scattered locations.
This primitive-looking shark has changed very little, coining the nickname "living fossil." Some refer to it as an eel or snake, but it's anything but. It's a poor swimmer, first of all, unlike the graceful eel/snake. These small animals also pack 300 smaller, razor-sharp teeth in 25 rows of teeth, with jaws ending at the end of the fish's head.
In Suruga Bay, Japan it has been commonly found at depths of 50–200 m (160–660 ft). It has rarely been seen on the surface. In 2007, fishermen caught a species, alive, and moved it to a nearby marine park. However, it died hours afterwards.
Unlike its South African relative, C. africana, it sports more vertebrae (160–171 vs. 147) and more turns in the spiral valve intestine (35–49 vs. 26–28). It also has a longer head, shorter gill slits, and larger overall size.
Yup, just like that.
Due to its diet, it is hypothesized that these animals vertically migrate up the water column every night, taking part in one of the largest migrations in the world.
No worries, though.
It's highly specialized for such a trek, and for life in the deep ocean. It has a reduced, poorly calcified skeleton, and an enormous liver, which helps it maintain neutral buoyancy with little effort. It has an "open" lateral line, where the mechanoreceptive hair cells are exposed; it's one of the few sharks with this "open" line.
Like many sharks, it probably is preyed upon by bigger sharks. Parasites also plague this shark, the most common being a tapeworm in the genus Monorygma, the fluke Otodistomum veliporum, and the nematode Mooleptus rabuka.
Be glad you aren't a frilled shark, pregnant moms. Otherwise you'd be carrying that little bean around for years... literally.
Their litter size varies from two to fifteen, and no breeding seasons has been determined.
They are occasionally caught as bycatch, but due to their small size have no economic value. In fact, they are rarely encountered alive, and thus pose no danger to humans... except some scientists have been known to cut themselves on their sharp teeth. The IUCN has assessed this animal as "Near Threatened," as even a few catches may harm the population, which has a very slow reproductive rate.