I was browsing around YouTube for cryptozoology videos (there are more amateur videos of "monsters" out there than you can shake a stick at) when I ran across a clip from a Japanese news show about a "sea dragon."  Intrigued, I did a bit of research, and learned about the frilled shark.

The frilled shark in the Japanese video is holding itself in a very unusual posture.  This is most likely caused by, or connected to the reasons for, it having ventured out from the depths.  As you can see from the video, the frilled shark is in very shallow water.  These are a benthic species, living deep within the ocean's depths.  

Either it was sick, which drove it to the shallows, or it was injured on its way up, which accounts for its odd posture.  The shark proved to be a pregnant female, which was rushed to a nearby marine park, where it was kept in a saltwater tank.  Sadly, it died within a few hours, as you might expect from an animal adapted to the pressures and cold temperatures of the deep ocean.

Frilled sharks are one of the world's "living fossil" breeds.  Much like the coelacanth, it was thought to be extinct, until it was rediscovered in the sea off Japan in the 1800s.  The frilled shark has barely changed in the millions of years since it first appeared in the fossil record.  

It resembles an eel, but with an extensible jaw and a mouthful of needle like teeth.  Its digestive system is very flexible, which means that (like so many other deep sea oddities) it can swallow meals much larger than most other animals.  One frilled shark captured in Africa was found to have swallowed another shark just slightly less than half its own size.

Some experts believe that frilled sharks may be responsible for legends of sea serpents and sea dragons.  Japan and China have a long history of aquatic dragon myths, and there is also the famous "here be dragons" legends on the edges of historical European maps.  Although a frilled shark is between three and five feet long, many sailors know better than to let the truth get in the way of a good yarn.

Frilled sharks are one of a myriad of species which are threatened by deep sea trawling.  Frilled sharks are often brought up by trawlers fishing for bottom dwellers like cod and shrimp.  A trawl is a large net which drags along the ocean floor, bringing up whatever can't manage to escape.  By the time it reaches the surface, everything in its catch is dead or fatally injured by the sudden pressure change from the bottom to the surface of the ocean.  

Trawling is one of the most damaging methods of fishing, and has led to ecological disruption on a grand scale.  Trawling is also a significant contributor to overfishing in areas like the North Sea and the Grand Banks.  Because of the destruction to their numbers caused by being dragged up as bycatch, frilled sharks are currently classified as "near threatened," which means that it is likely to be bumped up to the "threatened" list in the near future.