27. 08. 2026 Will Steen

What is the deepest living fish?

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The deep Ocean has some of the least familiar and harshest environments on the planet. Which animals can be found here? What is the deepest living fish?

The Ocean is deeper than you think. On average, it is 3,700m (12,139 ft) deep. At its deepest point, the weight of the water above would be like trying to hold a blue whale in your hand.

The deeper into the Ocean we travel, we lose the energy giving light of the Sun, lose temperature and increase pressure. As the pressure builds, life becomes fundamentally more difficult. There is a limit to how deep Ocean animals can live.

How deep in the Ocean has any animal holding its breath gone?

Some of the most successful animals in the Ocean still rely on breathing. Dolphins, whales, seals and turtles all have to fill their lungs with air from the surface, as human swimmers do.

Despite this, some lung-bearing animals still venture deep into the Ocean.

What is the deepest a reptile has gone?

There are only a few reptiles to be found in the Ocean now – most of them are turtles. Like birds and mammals, reptiles have lungs to fill with air, tethering them to the surface.

That doesn’t stop the deepest diving turtle: the leatherback turtle (Dermochelys coriacea), the largest turtle in the world.

In 2006, a tagged leatherback turtle named T2 dived to a depth of 1,280m (4,200 ft) southwest of Cape Verde. Impressive. But no turtle can keep up with the mammalian divers.

Leatherback turtle is the deepest diving reptile.

What are the deepest diving mammals in the Ocean?

The sperm whale (Physeter macrocephalus) is renowned for its deep-diving exploits to hunt giant squid. One tagged individual was recorded reaching 1,202m (3,943 ft) in the Atlantic, but research using hydrophones to track the clicks sperm whales produce while hunting estimated dives as deep as 2,094m (6.870 ft).

Southern elephant seals (Mirounga leonina) are the most surprising champions of the deep Ocean. Large and clumsy on land, they dive up to 2,388m (7,834 ft) in some of the least forgiving waters on the planet; the Southern Ocean. Recent research has shown that elephant seals will go to sleep on these dives, spiralling gently downwards during their naps. How else do you sleep when you spend 8 months at a time at sea?

But the title of deepest diving mammal, and deepest diving animal with lungs, belongs to the Cuvier’s beaked whale (Ziphius cavirostris). One tagged whale ventured to a depth of 2,992m (9,816 ft) in dives recorded lasting as long as 137 minutes.

Pretty impressive, but most marine animals don’t have to come up for air. So, how deep can they go? Let’s start with one of the most successful and long-standing marine families: the sharks.

What are the deep-dwelling shark species? 

It’s very rare to find elasmobranchs below 3,000m (9,842 ft), only a few species can do it (we look at why later). The Greenland shark (Somniosus microcephalus) is the longest living vertebrate in the world, has been found as deep as 2,992m. A leafscale gulper shark (Centrophorus squamosus) was captured alongside a pale ray (Bathyraja pallida) at a depth of 3,280m.

Greenland shark is the longest living vertebrate

How deep was the deepest shark found?

The Guinness World Records  and most online sources give the title of deepest shark to the Portuguese dogfish (Centroscymnus coelolepis), with a recorded depth of  3,700m (12,139 ft). 

This is tied with another distinctive shark, the cookie-cutter shark (Isistius brasiliensis), also recorded at 3,700m. But these are not the deepest elasmobranch.

A ray, close relative of the sharks, was recorded even deeper – a Bigelow’s ray  (Rajella bigelowi)  was found at  4,156m (13,635 ft).

They could possibly be found deeper: while setting the record for a manned dive in 1954, legendary deep-sea explorer Lieutenant Commander Georges Houot  took an image of an unidentified dogfish, with their depth estimated as just over 4,000m (13,123ft). This could be another Portuguese dogfish, but there is no verifiable depth recorded, so it is not acknowledged as an official sighting.  

How deep can octopus live?

Most octopus like the shallow, coastal waters of the world. But not all. Dumbo octopus (Grimpotethis sp.) are deep-living octopus known for swimming using the fins on the sides of its mantle, making it “fly” like the fictional elephant. In 2020 researchers found a record-setter in the depths of the Java trench off Indonesia, at a depth of 6,957m (22,824 ft).

Like their coastal cousins, these octopus live on and near the seafloor. Finding one nearly 7,000m deep in the Ocean means octopus can live on 99% of the seafloor – only 1% is deeper than 7,000m.

In other words: the deepest parts of the Ocean only make up a very small fraction, and there is very little out of reach for their many arms.

How deep in the Ocean was the deepest fish ever found?

In 1970, a species of cusk eel (Abyssobrotula galatheae) was caught in an open trawl net that went 8,370m (27,460 ft) deep. Although it was hailed at the time as the ‘deepest fish ever found’, we have no way of proving it was caught at that depth, not as the net went down or came up. Therefore, we can’t say for sure this was the deepest fish.

The cusk eels (Ophidiidae) are one of only two fish families found below 6,000m (19,685 ft). The other are the snailfish.

Imagine a tadpole that is half a metre long and you have a good likeness of a snailfish (Liparidae). They are a family that can be found in shallow coastal waters, and seven different Ocean trenches, the largest depth range of any family. The snailfish are the champions of the deep.

In 2017, a new species of snailfish was described. The Mariana snailfish (Psuedoliparis swirei) is named after its home: the deepest trench in the Ocean, the Mariana trench, about halfway between Japan and Australia.

Initially it was found 7,966m (26,135 ft) down, but later that year researchers found one even deeper at 8,178m (26,830 ft).

Even that isn’t the deepest. A different species of snailfish with no common name, Psuedoliparis belyaevi, was recorded by remote video cameras in 2023 at a depth of 8,336m (27,349 ft) to take the crown of deepest fish in the world. For now.

Below the depth limit of the snailfish there is over 3km (1.86 mi) more water to the deepest part of the Ocean. What, if anything, can survive these depths?

The deepest fish in the Ocean. Posted by Ocean Generation, leaders in Ocean education. — Credit: Cusk eel by NOAA/MBARI, Mariana snailfish by DOI:10.11646/zootaxa.4358.1.7

What are the deepest living animals in the Ocean?

On the 23^rd January 1960, humankind took a trip to the deepest part of the Ocean for the first time ever. The bathyscaphe Trieste, carrying Jacques Piccard and Don Walsh descended nearly 11,000m (36,089 ft) down. When they reached the bottom, Jacques Piccard looked out of the window into the abyss and saw, despite everything, a flatfish “resembling a sole”.

Don Walsh recalled stirring up a lot of sediment, that remained the whole 20 minutes they were on the bottom. He said “We could see nothing. It’s like somebody painted the front of the window with white paint.” Not ideal for observing new Ocean life.

Neither Don Walsh or Jacques Piccard were biologists, and they were looking out through a tiny porthole into murky dark waters. In the years since, this sighting has been disputed, and is no longer considered a fish. But they had seen something. What was moving in the murk?

What did the first dive to the bottom of the Ocean see?

They didn’t see any fish. The most likely explanation for the “sole” they saw is an animal that can be found even at these deepest corners of the Ocean – a sea cucumber. An expert in trench biology suggested the species Galatheathuria aspera, which is white and oval shaped.

It showed that complex life had reached even here, the very bottom of the Ocean. More recent research has confirmed this.

Bathyscaphe Trieste,
a deep-diving
research submersible — Credit: U.S. Navy Electronics Laboratory, San Diego, California

What is the deepest animal ever found in the Ocean?

The deepest animal yet recorded is a species of giant amphipod: think of the sandhoppers that bounce around when you move some old seaweed on the beach, but over 30cm (11.8 inches) long.

A species of amphipod, Hirondellea gigas, has been found 10,897m deep. 185 of them were collected over a 3-hour bait deployment, suggesting that even at the bottom of the Ocean there is a surprising abundance of life.

The deep dive: What limits how deep Ocean animals can go?

For the air-breathing mammals and reptiles, the constraints are clear – they must return to the surface to breathe. The same is not true of sharks and fish.

By assessing the number of species of elasmobranchs (sharks and rays) we find at different depths, researchers predicted the maximum depth we would find a shark/ray at to be 3,893m (12,772 ft). The number of species decreases as we go deeper in the Ocean. The rate at which species decrease gives a rough idea of when there will be no species.

That number is an estimate, but the same method predicts bony fish to a depth of 8,350m (27,395 ft), which is also remarkably close to the actual depth they have been found. But what is preventing these animals from venturing deeper?

The secret may lie, ironically, with a compound used to enable living at depth.

What is TMAO?

Trimethylamine N-oxide, or TMAO, stabilises proteins in a fish’s body to help them retain their structure and function even at depth. Think of it as a mini engineer, preventing damage to the fish. Fish found deeper have higher levels of TMAO to battle the larger pressures. Makes sense.

But you can have too much of a good thing. Too much TMAO means the water balance gets disrupted. As a general rule, water travels to places where there is lower concentrations of water.

If there is too much TMAO in fish tissues, that lowers the concentration of water in the tissue below the concentration of water in seawater. Too much TMAO means water will start entering the fish and ‘drown’ it.

But if both sharks and fish face this issue, why are sharks found so much more shallow?

The deepest animal ever found in the Ocean is a species of giant amphipod — Credit: Daiju Azuma/Wikimedia Commons

Why are sharks not found deeper?

All findings suggest that elasmobranchs can be found up to and maybe just over 4,000m (13,123 ft) deep, but no further. Why are one of the Ocean’s most successful inhabitants limited to half its territory?

Ocean animals have to be careful about staying hydrated. As they are in constant contact with water, it is harder to retain the water they need to survive.

Sharks do this by retaining urea – a waste product excreted in urine – in higher concentrations to keep their tissues similar water levels with the seawater (some can change their body function to move between fresh and salt water – read more here).

They effectively make themselves as salty as the sea, so they don’t lose water. However, urea (like water pressure) can affect and damage proteins, making them malfunction.

So, sharks employ the mini-engineer TMAO here to counter the effects of the high urea levels on their proteins.

This means sharks have higher levels of TMAO in the shallows, so when they increase TMAO levels to survive in the depths they reach that critical level of TMAO concentration sooner.

Why do fish have a depth limit?

Fish don’t retain urea, they excrete it, which means they have to constantly drink seawater and use energy getting rid of the extra salt. It also means they don’t need TMAO to counter the effects of high levels of urea.

Fish then don’t need to increase TMAO levels until they are getting deep, so can reach deeper as their TMAO is only countering the effects of depth.

The maximum levels of TMAO allow fish to exist up to approximately 8,200m (26,902 ft) which lines up with observations. Going deeper would mean either the pressure of the water breaking the very molecules life relies on or bursting from water rushing into an over-salty fish.

No wonder the fish leave that last 3,000 m (9,843 ft) alone.

The Ocean is very deep, but still connected

Every record here comes with an asterisk – it is the deepest so far. Until recently we thought the depths were empty, but now we are discovering more species here than ever before: over 1,000 new species in a single year.

This is a world we are still only just beginning to understand, yet it is not separate. The deepest known animal, the amphipod Hirondellea gigas, has bacteria in its gut for digesting wood and plant matter that sinks from the distant land above.

Everything in the Ocean, from the air breathing divers to the deepest amphipods, are connected with our surface world. As we are to it.

Why are sharks not found deeper in the Ocean: Explained by Ocean Generation.

Cover image: The University of Western Australia

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Will Steen

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11. 08. 2026 Will Steen

How accurate is Shark Tale?

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Shark Tale was DreamWorks’ underwater adventure released in 2004, and is a real nostalgia hit.

But with the rose-tinted glasses removed we ask: How accurate is Shark Tale? Let’s start by looking at the characters:

**What Ocean creatures are the characters of Shark Tale? (in order of accuracy)**

Most accurate characters in Shark Tale

Sykes is a long-spine porcupinefish (Diodon holocanthus). Visually very accurate, bonus points that he ‘puffs’ up using water, rather than the usual mistake of making him puff up using air. 10/10

Oscar is a blue-striped cleaner wrasse (Labroides dimidiatus). Cleaner wrasse are indeed the cleaners of the reef, picking off dead skin and parasites, which he would eat. Oscar not having a fear of sharks would be accurate to his species, as they also clean sharks. 9/10

Crazy Joe is a hermit crab. His larger left claw singles him out as a left-handed hermit crab, and his striped antennae and relatively large size point to the giant hermit crab (Petrochirus diogenes). 8/10

Don Lino, Lenny and Frankie and most of their ‘mob’ are great white sharks (Carcharodon carcharias). The distinct countershading, strong jaws and notorious dorsal fin sell it, although there is a lack of claspers (see below). 7/10

The whales at the whale wash all appear to be sperm whales (Physeter macrocephalus). While not impossible to find sperm whales around a coral reef, it is less likely than a humpback or other whale species. Sperm whales specialise in diving deep for their food, not usually spending time in shallow, coastal waters where you would find a reef. They look right, just wouldn’t likely be there. 6/10

Shark Tale characters that missed the mark

Angie is an angelfish, but it isn’t clear what species she is. Her colouration most closely matches a pygmy Japanese angelfish (Centropyge interrupta), but it isn’t a strong match. 5/10

Ira Feinberg, or Don Feinberg, has markings identifying him as an elderly leopard shark (Triakis semifasciata). Leopard sharks are a lot smaller than great whites and also not found on coral reefs. 4/10

Ernie and Bernie, the Rastafarian jellyfish henchmen, fall into the same generic limbo that the Finding Nemo jellyfish do. The closest likeliness is a mauve stinger (Pelagia noctiluca) or a purple-striped sea nettle (Chrysaora colorata). Either way, the skeleton x-ray animation and sounds of electricity are misleading. Like bees and wasps, jellyfish stings are injections of venom rather than anything electric. 3/10

Luca is, judging by size, a Giant Pacific octopus (Enteroctopus dofleini). No other octopus comes close to the size of a great white. But these octopus are not found on coral reefs, preferring colder waters from California to Alaska and round to Japan. Generally, they are a rust-orange rather than Luca’s dark green colouration. We talk about his mouth later. 1/10

Lola is allegedly a lionfish. In character maybe – they are voracious predators, ambushing anything that comes across their path. Unfortunately, Lola doesn’t look much like a real lionfish. She is missing the characteristic spines and has no tentacles above her eyes or below her mouth. Lionfish don’t have a skinny waist in real life. 0/10

Are coral reefs underwater cities?

The opening shows off the base premise of the film: that a coral reef is a big underwater city. We love it.

Coral reefs house a huge variety of life, with an estimated 25% of marine species dependent on coral reefs. Small fish live in the nooks and crannies of coral and use it to shelter from predators such as the sharks, exactly how it is shown in Shark Tale.

At one point, a fish is dumping its rubbish into another fish’s mouth. This is key to how a coral reef functions. The clear blue water we love is like a desert for those living in it – clear because there is very little food floating around. On a coral reef, all the waste is recycled – one fish’s garbage is another fish’s food.

Coral reefs are underwater cities. Posted by Ocean Generation

Do whale washes exist in the Ocean?

Blue-striped cleaner wrasse such as Oscar do indeed carry out cleaning services on the reef, but for a much more varied clientele than just whales. The core concept of the whale wash is real, but there are some details that go astray in the movie.

1. The Whales. These cleaning stations are more commonly for larger fish and marine reptiles such as turtles. Whales and other cetaceans can use other skin care routines, such as rubbing on stones or leaping out of the water. To make Shark Tale more accurate, we would make it a Ray Rinse, a Shark Scrub, or the Fish Freshen.

2. The Cleaning. Oscar is a tongue scrubber in the film, but most cleaning would be focused on the skin – picking off parasites and dead skin and sometimes venturing into the mouth. He certainly wouldn’t use a brush, instead would be using his mouth. Maybe better they left that out of the film.

3. The Staff. Cleaning stations on the reef can have lots of different staff, from cleaning wrasse like Oscar to cleaner shrimp. There were a few in Shark Tale that you wouldn’t find on the real reef.

Turtles are customers, not cleaners.
Dolphins, whether real or sharks in disguise, wouldn’t be found at the cleaning station
Electric eels wouldn’t be anywhere near a coral reef, as they are freshwater fish. The only electric fish in the sea are the torpedo rays

Cleaning services exist on a coral reef. Posted by Ocean Generation, leaders in Ocean education.

What are the sharks in Shark Tale missing?

One anatomical inaccuracy shared between Shark Tale and its reef-based rival Finding Nemo is an important piece of shark missing. Don Lino and co are a little short down below.

Male sharks have two adapted extensions of their pelvic fins called claspers, which they use for mating. Just like our friend Bruce, a quick look at any of the sharks in Shark Tale leads to questions of immaculate conception. Maybe, as some sharks have been known to do, the sharks on Southside Reef are pros in asexual reproduction (producing young with only one parent). Or perhaps we have a cast of Carcharodon (great white genus) drag kings.

Male sharks have claspers. Posted by Ocean Generation. — *Illustration by Chris_huh via Wikimedia Commons*

Do octopus have mouths?

Luca is, judging by size, a Giant Pacific Octopus. There is one glaring error – as with all cephalopods, octopus have their mouths on the underside of their bodies, which house beaks. Giant squid (Architeuthis dux) have the largest beak in the animal kingdom.

Luca’s top-side trap is useful for animators to create recognisable emotions and speech (and create a brilliant background moment of Luca pouring and trying to drink tea) but a miss for accuracy.

**Who is in the Shark Tale mob?**

Don Lino, Frankie and Lennie are part of the great white shark family running a mob at odds with the reef. But their mob doesn’t make much sense.

Great white sharks do not typically socialise, and certainly don’t hang out with family, although new research does suggest that some populations do have socialite sharks, in South Australia and Guadalupe Island, Mexico.

The great whites are joined by some other sharks, leopard sharks like Ira Feinberg and great hammerheads (Sphyrna mokarran). Great white sharks don’t usually like other sharks and in fact are known to eat smaller species like leopard sharks.

The swordfish (Xiphias gladius) at the table would have similar anxieties. Great whites aren’t known to eat them, but their cousins the shortfin mako do. Great whites are unlikely mobsters, who don’t have a close family and have few natural allies.

The most likely mobsters are the orca (Orcinus orca). In the wild, orca maintain close family ties and cooperate to hunt and protect each other (and they have accents). A recent video showed a new example of this – one orca holding a sunfish still while another rams it. They can then eat the bits that fly off. Brutal.

But the orca in Shark Tale aren’t the orca of our Ocean. In the film they are goofy and scared, fainting when Oscar talks to them. In the real world, they eat swordfish and they are also known predators of great whites. They flip them upside down into a catatonic state called tonic immobility and then remove and eat their rich livers, leaving the rest. In reality, the orca would sit at the head of the table, ruling the Ocean mob.

Seabirds often harass other birds. Posted by Ocean Generation.

What other animals belong in an underwater mob?

If we were going to re-make Shark Tale (live-action reboot anyone?), what animals would we have in our orca-led mob? Frigatebirds, skuas and jaegers are seabirds that harass other birds to regurgitate their food, chasing and bullying smaller species such as terns.

There are excellent fish con artists. The bluestriped fangblenny (Plagiotremus rhinorhynchos) is dressed the same as Oscar’s blue-striped cleaner wrasse, but instead of cleaning will bite a chunk of flesh off. Butterfly fish have a dark eyespot towards their tail, to confuse predators which way they are facing.

Some fish are just as territorial as any mobster. Damselfish are underwater gardeners, cultivating their favourite algae, which they tend to diligently. They will protect their patch enthusiastically against all odds and any size of intruder. The same can be said of the Titan triggerfish (Balistoides viridescens). Ask any SCUBA diver – Titans demand respect. They fear nothing, and will regularly chase and bite large sharks such as tiger sharks.

The mob in Shark Tale is based around a species that doesn’t like family, would eat some of the species and could be eaten by others. There are a lot of good other marine mobsters to choose from.

**Do sharks live on the Titanic?**

The main gangster hangout in Shark Tale is none other than the wreck of the Titanic.

Wrecks are popular hangouts for fish and the large predators that frequent natural reefs. In fact, research suggests that wrecks could attract more travelling predators than natural reefs.

BUT. The real-life wreck of the Titanic is sat at 3,800m (12,500ft) deep, in the Northern Atlantic. Most of the mob could live that far north, but the depth would be an issue. Sharks are not generally deep-living marine creatures.

This image is from a study investigating the depths different shark species spend time at. White sharks were tracked to a maximum of 1277m (4,189ft). The deepest confirmed sighting of a large shark is a sleeper shark (Somniosus sp.) that was spotted by a remotely operated vehicle (ROV) at 2647m (8,684ft).

There are no large sharks in the Titanic. Scientists hypothesise that some elements of shark biology may prevent them from living in the deep, which we can explore another time.

How deep do sharks go - Explained by Ocean Generation. — Illustration via DOI: 10.1126/sciadv.abo1754

Do great white sharks go to bed?

In the film, Lenny is excited to find a bed to sleep on while hiding with Oscar. Now, you may know great white sharks don’t sleep on beds, but did you know they don’t even stop swimming to sleep? Let’s talk shark sleep.

For sharks (and all fish) to breathe, they must have fresh, oxygen-rich water move over their gills, just as we need fresh, oxygen-rich air moving over our internal ‘gills’ – our lungs. Some sharks can do this while stationary – forcing water over their gills using a technique called buccal pumping.

Great white sharks are among a group of sharks that can’t do this – they don’t have the nostril-like structures called spiracles behind their eyes which allow it. So, white sharks must keep the water moving over their gills through their movement – known as ram ventilation.

Research around sleep in these sharks is still lacking – we don’t really know what sleep looks like for them. But we know they don’t curl up in bed.

Are great white sharks cold blooded?

As Frankie is dying after being hit by an anchor, he tells Lenny “I feel so cold”, to which his brother helpfully replies: “but we’re cold blooded”. Frankie’s last word? “Moron”. That is probably because Frankie knew that great white sharks actually aren’t cold blooded.

Most fish are ectotherms – their body temperature is entirely determined by the temperature of their surroundings. Humans, along with all mammals and birds, are endotherms – “warm-blooded”, maintaining a favourable internal temperature utilising the heat produced by metabolism. Great white sharks, along with the other lamnid sharks (salmon sharks, mako sharks and porbeagle sharks), tuna and the leatherback turtle, are mesotherms.

What is a mesotherm?

A useful setup of blood vessels keeps the heat produced by the muscles in the system, rather than removing it with the deoxygenated blood. This is known as counter-current exchange.

This intermediary between the two means they can raise their internal temperature above that of their surroundings, but they do not have the high metabolic demand of being truly endothermic. The advantage is that these fish can work faster – these are some of the fastest fish in the Ocean. The leatherback can stay deeper for longer on its feeding dives before it needs to return to the surface to warm up.

Not cold blooded, but not warm blooded either.

Great white sharks. Posted by Ocean Generation.

Do sharks eat everything?

After holding Angie in his mouth, Lenny ends up throwing up a whole host of fun things. One of them is a number plate. This is based on fact: license plates have been found in the stomach of tiger sharks. This particular license plate is actually the exact plate Hooper pulls out of a tiger shark in Jaws, and that is discovered in the teeth of a tiger shark in Deep Blue Sea.

Other items include a radio, a violin, a beach ball and a broom.

Tiger sharks especially are nicknamed the rubbish bins of the Ocean and have been found with all manner of strange things in their stomach. A fur coat, a coil of copper wire, an unopened tin of salmon and a suit of armour are all among strange things recovered from shark stomachs.

Conclusion: How accurate is Shark Tale really?

Some of the core elements of the film are brilliant. The framing of a coral reef as a city is one we love – capturing the essence of so many species living and working together. The whale wash is a lovely idea, although making it a turtle wash, shark wash or any other large fish would have been more on the money.

But the shark mob, the Titanic and Lola the “lionfish” knock the accuracy score way down.

Verdict: Sleeping with the fishes… the dead ones. – Luca, 2004