A wide variety of creatures dwell in the depths of the world's oceans, with sharks being some of the most mysterious. Although there's a vast array of fish in the sea, vulnerable shark species are still falling victim to a number of threats, resulting in rapidly thinning populations - with humans playing a major part in the destruction. According to a study by researchers at the Stellenbosch University in South Africa, ocean acidification is damaging shark populations by corroding the protective scales on the outer layer of their skin. With rare and endangered sharks becoming more scarce, the majority of us would be lucky to catch a glimpse of them in the wild at all.
Even if you do happen to stumble upon one, you might not even be able to tell that it's a shark at first, as not every shark out there resembles the stereotypical great white. The variety of sharks that reside in the open and coastal waters of the world are all majestic and unique in their own right, with biological oddities proving that nature is just as unusual as it is beautiful.
The mighty megamouth shark is actually a member of the filter-feeding shark trio, the other two being the whale shark and the basking shark - all of them have special plankton-luring luminous mouth organs that give them their advantage. Despite being the smallest of the trio, the megamouth shark can grow up to 18 feet in length, with nearly one-quarter of its massive body being occupied by its mouth alone.
Since its discovery in 1976, there have only been 69 confirmed sightings of this rare sea-dweller due to the fact that it resides primarily in the deep waters of the tropics.
The ghost shark, given the scientific name Callorhinchus milii, is a type of Chimaera, which branched off from sharks almost 400 million years ago. The ghost shark is now its own, singular entity residing in the waters off of Australia and New Zealand, and was caught on film for the first time by sheer luck during a deep-sea exploration.
Adding to its status as an underwater oddity, the male has a retractable penis-like sexual organ on its head.
A deep-water dweller by nature, the goblin shark is a rarely seen oddity. Its lineage is ancient and dates back 125 million years, earning it the nickname "living fossil."
It has a uniquely defined snout that resembles a rather nasty goblin, but its odd-looking, protruding forehead is actually remarkable, as it contains a special sensing organ full of jelly-filled pores called "ampullae of Lorenzini," allowing the shark to pick up the electric and magnetic fields produced by nearby prey.
The swell shark doesn't grow to great lengths, reaching a maximum of only 43 inches. It makes its home among the algae-covered floors of the subtropical Pacific Americas, where it hunts shellfish and other smaller, easily snagged fish. An interesting defense mechanism of this shark is that, when it's scared, it can bend its entire body into the shape of a "U" and suck up water into its stomach, markedly increasing its size and making it difficult to bite.