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With an average adult length between 8 and 15 ft to a maximum of 24 ft, the Greenland shark is the Arctic's largest fish. It is native to the north Atlantic and the Arctic and is the only shark to tolerate such temperatures throughout the year; its preferred range seems to be 30-50°F. It can be observed from the surface to depths of almost 7,218 ft. The Greenland shark is believed to be an opportunistic feeder and a scavenger primarily; if prey is too large to swallow whole, it is able to pin it in place with pointed upper teeth and cut round "plugs" from it with wide, curved bottom teeth by swinging its head in a circular motion. 90% of the observed Arctic population are host to the parasitic copepod Ommatokoita elongata, which consumes its corneal tissue and causes partial blindness, but its habitat and depths renders its sight useless. The only confirmed predator of the Greenland shark is the sperm whale, although it is also known to be cannibalistic in the presence of individuals deceased or in distress. Currently classed as Near Threatened and taken as bycatch, it has been historically targeted for its rich liver oil but the extremely high concentration of urea and trimethylamine oxide in its flesh renders it toxic. There is very limited data at present on its lifespan except for a single scientific paper that showed a size increase of just over 2 inches in 16 years on one shark; this growth rate suggests that a fully grown Greenland shark could be over 200 years old, potentially making it the longest-living vertebrate on the planet.

Widespread throughout the world's temperate and tropical waters, the blue shark is a pelagic species that is usually encountered in the open ocean but can be spotted inshore where the continental shelf is narrow. It can be found from the surface (in cooler waters) to a depth of approximately 1148 ft (in more tropical areas) and is highly migratory; its movements seem to be based on reproduction and prey distribution. The blue shark's diet consists mostly of cephalopods, crustaceans and bony fishes, but it is also known to consume sea birds and cetaceans (possibly as carrion). Its colouration - deep blue on the dorsal side and bright white underneath - is camouflage in the open ocean and referred to as countershading. It is viviparous, with females delivering an average of 35 pups per litter (although the maximum recorded litter size was 135 pups) after a 9-12 month gestation. The skin of the female is three times thicker than that of the male, as the blue shark's courtship involves extensive biting from the latter. Adults can reach about 12.5 ft in length at their maximum. Though the blue shark is not a species targeted by commercial fisheries, it is frequently caught as bycatch: It is estimated that 10-20 million blue sharks are killed annually. It is also sought after by sport fishermen, and is currently classed as Near Threatened by the IUCN.

Found in the temperate waters of the northeastern Pacific from the intertidal zone to a depth of 394 ft, the big skate is the largest species to be found in North America with a maximum recorded length of 7.9 ft, although the average is usually no more than 5.9 ft. It feeds on polychaete worms, benthic fish, crustaceans, and molluscs. It is one of few skate species to have more than one egg inside each egg capsule, or mermaid's purse. The big skate is often taken as bycatch and is targeted by commercial fisheries in Alaska and California; it is listed as Near Threatened by the IUCN.

Native to the coastal tropical and subtropical waters of the Atlantic and the eastern Pacific, the nurse shark is a nocturnal species that spends the day resting under ledges or in reef crevices. Though it can be observed resting in close groups of up to 40 individuals, sometimes piled on top of each other, at night the nurse shark is a solitary hunter that seeks out stingrays, fish, molluscs, and crustaceans along the sea floor. It is also known to graze on algae and corals. The mouth is small but the nurse shark's pharynx is large and bellows-like, enabling it to suck in prey at a high speed. Adults can achieve a length of about 14ft, making it the largest in the Ginglymostomatidae (nurse shark) family. Despite its wide distribution and apparent abundance in certain areas, there is not enough data to determine its overall status at present, though it is believed to be vulnerable to human impact (including pollution and disturbance from tourism) and some fisheries.

Encountered in the Indo-Pacific from South Africa to Australia, the leopard whipray has a striking pattern of dark brown rings on its dorsal side that gave it its name. Like all species in the Himantura genus, known as the whiprays, it has a very long, thin tail that lacks a dorsal or caudal fin and can measure more than three times the length of its disc. Adults can reach approximately 5.9ft in width and a total length of about 13ft with an intact tail. Due to confusion with the closely related honeycomb and reticulate whiprays, the leopard whipray is not well known. It is heavily fished in parts of Indonesia for its meat and possibly other parts using bottom trawls, tangle nets, and longlines, and has not been classified by the IUCN at this time.

Named after the two large dark spots behind the pectoral fins that resemble military epaulettes, the epaulette shark is native to the waters of the western Pacific around New Guinea and northern Australia. It is one of 16 species of longtail carpet sharks and reaches an adult length of just over 3ft. Like all species in the Hemiscylliidae family it has a long, slender body that allows for it to maneuver into and around narrow crevices on the reef while hunting for its benthic invertebrate prey, which it may chew for several minutes. Its nocturnal habits and tendency to be caught in small tidal pools has led to a remarkable adaptation for survival in oxygen-depleted habitats: It can selectively switch off nonessential body functions for several hours with no ill effects, and, as a result, can even survive complete anoxia (oxygen deprivation) for an hour at temperatures as warm as 86°F. The epaulette shark doesn't usually swim unless escaping a predator, but rather "walks" along the sea floor by bending its body from side to side and pushing with its muscular pectoral and pelvic fins. These fins have reduced cartilaginous supports compared to those of other sharks, allowing for an increased range of movement and the ability to use them as limbs.

Found along the tropical and subtropical parts of the Atlantic and Pacific coasts of both North and South America as well as Africa's Ivory Coast, the lemon shark's name is derived from its coloration, which can appear a pale yellow. It is perfectly camouflaged for swimming over the sandy sea floor while hunting for bony fish and crustaceans, although it is also known to feed on sea birds, rays, and smaller sharks. Fully grown adults reach approximately 8-10ft in length. It is viviparous, with females giving birth to a litter numbering between 4-17 pups every other year after a 10-12 month gestation; the pups stay in and around the shallow "nursery grounds" in which they were born for several years before venturing further. The lemon shark is targeted by commercial and recreational fishermen and is particularly sought after for its fins, which fetch a high price in the shark fin trade. It is currently listed as Near Threatened by the IUCN.

Though their bodies resemble that of a shark, sawfish are a family of rays. The largetooth (or freshwater) sawfish is found in the tropical waters of the Indo-West Pacific, inhabiting the sandy or muddy bottoms of shallow coastal waters, estuaries, and even lakes, with some individuals spending their entire lives in freshwater. The rostrum, or "saw", features 12 to 22 large "teeth" on either side - teeth that, unlike those of sharks, are deeply embedded in their cartilaginous sockets - and can be used for digging for benthic invertebrates in the substrate as well as disabling schooling fish. Adults can achieve a maximum size of 21.5 feet. As with all species of sawfish, this species is listed on the IUCN Red List as Critically Endangered. Not only is it particularly prone to entanglement fishing gear and habitat destruction, the saw is valued worldwide as a souvenir or trophy. Extensive mythology surrounds the sawfish throughout its range: They have been regarded as totems and symbols of warfare, with weapons fashioned out of the rostrum and sawfish emblems adorning WWII vessels, and sawfish parts are in high demand in the Asian medicine and shark fin trades.

Also known as the Atlantic devil ray, this species is found mostly in the shallow waters of the western Atlantic from North Carolina to northern Argentina. Primarily pelagic throughout its range, the lesser devil ray feeds on planktonic crustaceans and small fish, which it funnels into the mouth using its distinctive cephalic fins. Unlike its relative the giant devil ray (Mobula mobular), the lesser devil ray's long tail lacks a spine entirely. Fully grown, it can reach a maximum width of approximately 3.9ft, and is ovoviviparous like all myliobatoid rays, with females giving birth to one pup per litter. It is a particularly fast-swimming species that can be observed leaping completely out of the water. Currently there is not enough data to determine its status, but it is taken as bycatch.

Found in the western Atlantic from Massachusetts to Nicaragua, the chain catshark is common throughout its range but rarely encountered due to its usual depth, which is around 120-750 feet in the north and deeper than 1,500 feet in the south. Like most species in the Scyliorhinidae family it is a small species, with adult females growing no larger than 1.7 ft long. During the day it can be observed resting on the rocky bottom, often close to man-made objects such as cables. It is a bottom feeder with a diet consisting of squid, bony fish, polychaete worms, and crustaceans. In 2005 Dr. Mikhail Matz, a professor of marine biology at the University of Florida, was the first to identify and document the chain catshark's previously unknown fluorescent properties; it is still unclear what purpose this serves.

A remarkable hunting technique of this active, fast-swimming shark gives it its common name: it will speed upward through a school of fish with its mouth open while spinning on its axis, emerging completely from the water. Although the maximum known size is known to be 10 feet, the average adult attains a length of just over 6 feet. Found in subtropical and warm temperate waters around the world except the eastern Pacific, the spinner shark forms schools, and the northwest Atlantic population migrates inshore during the summer months to feed and reproduce. Because of confusion with the blacktip shark, there is some uncertainty in the distribution data for this species. Throughout its range, particularly in the southeastern United States, the spinner shark is considered Near Threatened by the IUCN due to its popularity among recreational and commercial fisheries; it is prized for its fins, liver oil, flesh, and skin.

Common throughout nearshore Indo-Pacific reef habitats, the bluespotted ribbontail ray can be easily identified by its electric blue spots and two stripes on the tail. A small species that rarely exceeds 2.5 ft in total length, it hunts at night during high tides and retreats to the reef to shelter during the day when the tide recedes. Prey, usually benthic invertebrates and fish, are trapped by the ray's body and maneuvered towards the mouth by the pectoral fin disc. There are usually two - sometimes one - serrated venomous spines on the tail. Though currently abundant, the IUCN classes this species as Near Threatened due to the widespread destruction of coral reefs and fishing pressure.

The deepsea skate's depth range of between 1,148 and almost 9,528 feet makes it one of the deepest known species. It is found in the northern Pacific from California through the Bering Sea to the central coast of Honshu, Japan, and feeds primarily on benthic invertebrates. It is believed that females reach at least 5 ft. in size. As it is rarely encountered there is not currently enough data available to determine its status, though it is known to be taken as bycatch by deep commercial trawls and traps.

Native to coastal waters in the Eastern Pacific from central California to Chile, the swellshark is a nocturnal species that rests among the rocky reef during the day and hunts fish, crustaceans and molluscs at night. Adults reach an average length of about 3ft and are oviparous, with the female depositing only two egg sacks at a time among a rocky, algal-covered habitat. When threatened, it bends its body and grabs its caudal fin in its mouth before swallowing a large amount of water to double its size, making it difficult for a potential predator to bite or remove it from a crevice. It is also able to do this same behaviour with air if brought to the surface, and will let out a dog-like bark when expelling the swallowed water or air.

Named because it is usually seen swimming slowly at the surface while feeding, as if sunning itself, basking sharks are second only to the whale shark in size with an average adult length of 22-29ft. It is one of three species of filter feeding shark and the only one to use just the continual passage of water to trap its planktonic food against its gill rakers as it swims - it is believed to be able to filter 2,000 tons of water in an hour. It has a wide distribution throughout the world's boreal and temperate waters, although it is not known to be abundant. Due to its slow growth rate and long gestation, the IUCN Red List currently classes the species as vulnerable worldwide and endangered in the north east Atlantic and north Pacific, where it was heavily fished: The basking shark's liver can account for 25% of its total weight, and its fins are among the most valuable in the international trade.

Also known as the peacock-eye stingray, this species is native to the Amazon, Uruguay, Orinoco and Paraná river basins, and is a potamodromous stingray with its migrations taking place entirely in freshwater. It can reach a size of about 3ft, and like others in the Potamotrygon genus it has a venomous barb at the end of its tail. Although it is abundant throughout its known range, there is not enough data at present to determine its status.

A frequent sight in tropical Indo-Pacific reef habitats, blacktip reef sharks tend to have a very limited home range, remaining in the same area for years at a time. They are swift and active hunters, preying primarily on bony fish, cephalopods and crustaceans, and play a major role in the structure of the inshore ecosystem, where they are an apex predator. Like most species in the Carcharhinidae family it is viviparous, with females giving birth to 2-5 pups. Fully grown blacktip reef sharks can reach approximately 5ft in length.