O is for Oarfish

If the Loch Ness Monster turns out not to be a myth, it is probably a close cousin of the giant oarfish.

The serpent-like sea creature can weigh nearly 600 pounds and grow to lengths of about 56 feet, making it the longest bony fish. It has a silvery sheen, and a long, red fin runs the length of its body. The oarfish's eerie appearance has earned it different nicknames around the globe, including the "king of herrings," the "rooster fish" and the "ribbonfish."

Not much is known about these rarely seen inhabitants of the ocean's twilight zone. One video captured by a remotely operated vehicle (ROV) in 2011 shows an oarfish propelling itself through the water by undulating its dorsal fin. Researchers also spotted a hitchhiking parasitic isopod on its back.

Oarfish live in the ocean's mesopelagic zone—650 to 3,300 feet below the surface—but every now and then a few surface in the shallows. It is unlikely the fish are looking for food; their diet of krill and small crustaceans is harder to come by in shallow tropical waters. So what brings these behemoths out of hiding?

In some ancient traditions the smaller slender oarfish is known as a "Messenger from the Sea God's Palace" warning of impending earthquakes. Some scientists hypothesize that shifts in the continental shelf may create strong currents that force the creatures out of the deep sea. Others argue that seismic activity takes place too far away on the ocean floor to affect the oarfish.