50 Fun Facts About The Deep Sea

Which film director piloted a submersible alone to the bottom of the Challenger Deep in March 2012?

James Cameron made the dive in the Australian-built Deepsea Challenger, sinking for more than two and a half hours to reach the seabed.

Which deep-sea fish lures prey with a glowing bait that dangles from a modified fin spine on its head?

Anglerfish light their lure with colonies of glowing bacteria, and their jaws and stomachs stretch to swallow prey up to twice their own size.

Which crescent-shaped Pacific feature contains the Challenger Deep, the deepest known point in any ocean?

The Mariana Trench plunges almost 11 km, so its floor lies farther below sea level than the summit of Everest stands above it.

Which sea monster of Norwegian sailors' lore is thought to have been inspired by sightings of giant squid?

The Kraken was first described in a Norwegian glossary of 1646, and the giant squid that may lie behind the tales can grow more than 10 metres long.

Which fish from deep waters off Australia was voted mascot of the Ugly Animal Preservation Society?

The blobfish floats just above the seabed without swimming, because its jelly-like flesh is slightly less dense than water.

What name do scientists give the steady shower of organic debris that sinks into the deep ocean?

Marine snow carries energy down from the sunlit surface, and many animals of the dark water below depend on it for food.

Which deep-sea cephalopod, the only living member of its order, is named for its dark, cloak-like webbed arms?

The vampire squid drinks no blood: it feeds on drifting detritus, and its closest living relatives are the octopuses.

Which deep-diving mammal plunges more than two kilometres to hunt squid and makes the loudest sound of any animal?

The sperm whale often carries white scars thought to come from fights with giant squid, though no human has ever watched such a battle.

Which oceanographer co-led the 1985 French-American expedition that found the wreck of the Titanic?

Robert Ballard was given the ship time only after he had first surveyed two sunken nuclear submarines in secret for the US Navy.

Which deep-sea cephalopod, found even in ocean trenches, swims by flapping a pair of fins on its mantle?

The Dumbo octopus is named after Disney's flying elephant and, unlike most of its relatives, has no ink sac to squirt.

Which lobe-finned fish, thought extinct for about 66 million years, was caught alive off South Africa in 1938?

The coelacanth is more closely related to lungfish and four-limbed land animals than to ordinary ray-finned fish.

Bacteria at hydrothermal vents make food using energy from hydrogen sulfide instead of sunlight, in what process?

Chemosynthesis was named by Wilhelm Pfeffer in 1897, eighty years before whole animal communities built on it were found on the seabed.

The deepest ocean zone, found mainly in trenches below 6,000 metres, takes its name from which Greek god?

Hades ruled the underworld, and the hadal zone named for him covers under a quarter of one percent of the seafloor yet spans over 40% of the ocean's depth range.

What nickname is given to the ocean's mesopelagic layer, where the last faint daylight fades below about 200 metres?

The twilight zone begins where only 1% of surface light survives, and its base holds the SOFAR channel, the layer where sound travels slowest.

Which colour of light do most glowing sea animals produce, though a few deep-sea dragonfish also shine red?

Blue light carries well through seawater while red fades fast, so a dragonfish's red beam is short-ranged but invisible to most of its prey.

Which Southern Ocean mollusc is the heaviest invertebrate known and has the largest eyes of any animal?

The colossal squid can weigh about half a tonne, and it is the only member of its family armed with hooks on its arms and tentacles.

Which deep-sea crustacean, a relative of the garden woodlouse, can grow as long as 50 centimetres?

The giant isopod is built for famine: captive animals have survived more than five years without food.

In which bathyscaphe did Jacques Piccard and Don Walsh first reach the Challenger Deep in 1960?

Trieste was Swiss-designed and Italian-built, and it floated on tanks of petrol, a liquid that is lighter than water and barely compresses.

Which hydrothermal vent animal has no mouth or gut and lives on food made by bacteria inside its body?

The giant tube worm is also the fastest-growing invertebrate known in the sea, able to colonise a new vent and reach maturity in under two years.

Which Woods Hole submersible located a lost hydrogen bomb off Spain in 1966 and later explored the Titanic?

Alvin has made more than 5,000 dives since 1964, even though it once flooded and sank in 1,500 metres of Atlantic water.

Hydrothermal vents teeming with life were first found in 1977 on a rift named after which Pacific archipelago?

Near the Galápagos Islands, a geological expedition looking for warm seabed springs stumbled on dense animal communities that nobody had predicted.

What name is given to seabed vent chimneys that pour out clouds of sulfide minerals in superheated water?

Black smokers were first found in 1979 on the East Pacific Rise, and each chimney starts to grow when the mineral anhydrite settles around a vent.

Which deep-sea fish looks upward through a transparent, fluid-filled dome on its head?

The barreleye was long thought to have eyes fixed in place, until researchers in 2008 found that they can rotate forward to track prey.

Which deep-sea eel, also known as the gulper, has a loosely hinged mouth far larger than its own body?

The pelican eel can open its jaws wide enough to swallow a fish much larger than itself, and it was first watched alive in the wild only in 2018.

Which small deep-sea fish needs sockets beside its brain to hold the tips of its two longest lower teeth?

The fangtooth looks fearsome but is harmless to humans, and its family holds just two species with no known close relatives.

Osedax worms, first found in Monterey Bay in 2002, feed by boring into which part of dead whales on the seabed?

Bones give the genus its Latin name, which means 'bone devourer', and its females are more than 20,000 times larger than the males.

Which kind of fish has been filmed swimming more than 8,300 metres down in the Pacific's Izu–Ogasawara Trench?

Snailfish reach the surface intact when hauled up from such depths because, unlike many fish, they have no swim bladder.

Which tiny deep-sea fish, notably the genus Cyclothone, are thought to be Earth's most abundant vertebrates?

Bristlemouths are named for their odd, bristle-like teeth and are estimated to number in the trillions or even quadrillions.

The sea pig, which roams abyssal plains on enlarged tube feet, belongs to which group of echinoderms?

Sea cucumbers of this genus use their tube feet to gather organic matter that has settled on the seabed, churning up the mud as they feed.

Which ribbon-shaped fish, the world's longest bony fish, may be the source of many old sea serpent sightings?

The giant oarfish can reach about 8 metres, and its common name probably comes from its long, oar-shaped pelvic fins.

Which jawless, eel-shaped scavenger of the deep seabed defends itself by releasing huge amounts of slime?

Hagfish can also tie themselves in a knot and slide it along the body, scraping off the slime and wrenching free of a captor.

Which deep-sea fish stands above the seabed on long, stilt-like rays of its pelvic and tail fins?

The tripodfish touches down on its pelvic fins first, and it is one of the few fish of its genus ever photographed from a submersible.

The scaly-foot snail of Indian Ocean hydrothermal vents armours its shell and foot with compounds of which metal?

Iron sulphide makes this snail the only living animal known to build the metal compound into its skeleton.

Cold seeps on the deep seabed leak which gas that reacts with seawater to build carbonate rock and reefs?

Methane seeps are not really cold: the leaking fluid is often slightly warmer than the surrounding seawater.

What is the nightly rise of deep-water animals to the surface, by biomass the largest animal movement on Earth, called?

Diel vertical migration puzzled World War II sonar operators, who saw a false sea floor that sat deep by day and rose at night.

What name is given to the dense, extremely salty underwater 'lakes' that collect in hollows of the deep seabed?

Brine pools are three to eight times saltier than the sea around them, and animals that stray in can suffer toxic shock.

Which seafloor feature, where new crust forms as plates spread apart, is Earth's longest mountain range?

The mid-ocean ridge system links up through every ocean, which is how it comes to outstretch any mountain chain on land.

The word abyss, which gives the ocean's abyssal zone its name, comes from a Greek word meaning what?

Bottomless in Greek was 'abyssos', built from 'a-' (without) and 'byssos', a word for the bottom of the sea.

Researchers from which country captured the first images of a living giant squid in its natural habitat in 2004?

Japan's Tsunemi Kubodera and Kyoichi Mori hung a baited camera line 900 metres down, where an 8-metre squid attacked the bait and tore free hours later, leaving a tentacle behind.

Roughly how many times greater than at sea level is the pressure at the bottom of the Challenger Deep?

About 1,000 times surface pressure works out to roughly eight tons pressing on every square inch of a submersible's hull.

Which private-equity investor piloted the submersible Limiting Factor to the deepest point of all five oceans?

Victor Vescovo had already climbed the highest peak on every continent and reached both poles before turning to the ocean floor.

Which former NASA astronaut, the first American woman to walk in space, also dived to the Challenger Deep in 2020?

Kathryn Sullivan made her spacewalk in 1984 and her ocean dive in 2020, and in between she ran NOAA, the US ocean and weather agency.

In which cable-lowered steel craft did William Beebe and Otis Barton descend half a mile off Bermuda in 1934?

The Bathysphere had no power of its own, so Beebe described the glowing animals he saw over a telephone line to the surface.

The International Seabed Authority, the regulator of deep-sea mining, has its headquarters in which country?

Jamaica hosts the body in Kingston, where it first met in 1994 on the very day the UN's Law of the Sea convention came into force.

Xenophyophores, which can grow to 20 cm across on the deep seabed, are remarkable for each consisting of what?

Single cells with many nuclei, they build a shell around themselves by cementing together grains of seabed sediment.

What are the egg-sized, metal-rich lumps littering abyssal plains that deep-sea miners hope to harvest called?

Manganese nodules form in concentric layers around a core, and they are prized for the nickel, copper and other metals locked inside.

The Bloop, a powerful sound picked up by Pacific hydrophones in 1997, was later traced to what?

An icequake was the verdict by 2012, ending speculation about a huge animal; the sound had carried to sensors more than 5,000 km away.

Which American oceanographer, nicknamed 'Her Deepness', walked untethered on the seabed off Oahu in a JIM suit in 1979?

Sylvia Earle went on to become the first woman to serve as chief scientist of the US ocean and weather agency.

The Challenger Deep is named after two survey ships that sailed under the flag of which country?

Britain sent out two ships named HMS Challenger: one first located the deep in the 1870s, and the other fixed its record depth in the early 1950s.

What are the light-producing organs that stud the bodies of lanternfish, hatchetfish and many deep-sea squid called?

Photophores on an animal's underside can match the faint light from above, erasing the silhouette a predator below would otherwise see.