Lurking in the cold depths of the ocean, the megamouth shark swims with his mouth open wide to filter plankton from the water. They spend most of their lives down here in the dark, at times
descending to fifteen thousand feet below. However, a tag placed on a megamouth in the early 1990s provided evidence that this shark follows 24-hour cycles, spending its days in deep water and emerging at the surface at night.

Similar to Greenland sharks and other creatures of the depths, the megamouth exhibits deep-sea gigantism, with one specimen found off the coast of Taiwan measuring more than 23 feet long. But with pectoral fins smaller than its enlarged head, and an asymmetrical caudal fin, it is not a skilled swimmer. A shark of this size would be enough to make many terrified. And yet it poses no threat to us. It is one of only three known filter-feeding sharks, including the basking shark and whale shark, and like them it cruises through shoals of krill with his mouth wide open.

What's unique to this shark however is its ability to push out its jaw and suck the prey inside. There are fifty rows of tiny hooked teeth on each jaw, though it only uses the first three rows. The inside of the mouth is covered with light-producing organs called photophores that are believed to attract small prey. This is a useful tool to possess down in the abyssopelagic zone as there is no penetration of natural light from above.

Despite being among the largest sharks in our seas, the mega mouth was not discovered for the first time until 1976 when a US Navy research vessel hauled up an adult male specimen of the coast of Hawaii. The discovery of a shark like this was so unexpected that a new family, genus and species was created just to classify a fish so strange. Since that day, there have only been around fifty confirmed sightings. This raises the question what other deep-sea giants are out there waiting to be discovered.