Original subtitles

[intense music]

- Tonight, the search for one of the most terrifying creatures

said to prowl the open seas.

- Stories of the Kraken have been around

for centuries.

- It was the size of an island

and its sole purpose was to feast on human flesh.

- There are countless alleged encounters

between sailors and the Kraken,

but descriptions of this creature vary wildly.

- There were tentacles coming out of the water,

wrapping around people,

pulling them back into the ocean.

- All they saw was rapidly moving water,

a vortex that was getting bigger,

and that adds to the mystery.

- Now, we explore the top theories

surrounding this fearsome creature.

- He says, "I have found proof that the Kraken is a real beast

and did exist about 200 million years ago."

- Every time we go exploring in the deep sea,

we find new creatures, and some of them are big.

- With that much isolation and open ocean,

you can imagine that

sailors would start to kind of lose their grip on reality.

- Could the legendary Kraken possibly be real?

[epic music]

- [Laurence] As long as people have sailed the open seas,

[thunder crashes]

they've told tales of encounters

with deadly, man-eating sea creatures.

- Both Jewish and Christian texts reference the leviathan,

which is a giant sea creature that was incredibly dangerous

and eventually killed by God

so that they would not reproduce.

- In the epic poem "The Odyssey,"

Homer describes a deep-sea beast with six heads

and triple rows of teeth that devours passing sailors,

including half of Odysseus's men.

- All cultures that have grown up

along the oceans or the seas

have tales of massive sea animals.

That's why from the 10th century to the 17th century,

maps had all of these sea monsters drawn

and written around the sides.

If you stay within this, you're going to probably be okay,

but if you go out, you could run into something

that could literally swallow your boat whole

and drag you to the bottom of the ocean.

- [Laurence] But over the centuries,

arguably the most feared sea monster of all

becomes known as the Kraken.

In 1180, writings from a Norwegian ruler

placed the beast in Scandinavia.

- King Sverre specifically warned people

against this monster that was menacing ships

between Norway and Iceland,

and he tells us it was the size of an island,

and its sole purpose was to feast on human flesh.

- Later on in the 1500s,

an archbishop named Olaus Magnus

describes the Kraken as having long horns

and built thick like a tree with fiery red eyes.

And this is based on accounts

that he's heard from sailors

whose ships have been attacked at sea.

This is an animal that will sink your ship.

- After the invention of the printing press ,

this description gets distributed far and wide

and is taken aboard ships

that are bound for destinations

like China or even the West Indies.

- [Ryan] Naturalist Pierre Denys' illustration

of the Kraken is arguably the best one of all time

because you have a British warship

being attacked by this massive beast

with all of these tentacles

and it appears to be winning,

so you have to go out there knowing

that this thing could, at any point, take you

to the bottom of the ocean.

- [Laurence] These stories aren't just

centuries-old fables.

Such alleged attacks also occur in modern times,

including one harrowing encounter during World War II.

- [Kavitha] In 1941, the Germans attacked

a British steam liner, the SS Britannia,

just about 750 miles off the coast of Sierra Leone.

Hundreds of passengers are forced to abandon ship

in just a handful of lifeboats, and they're cast adrift

for several weeks, if not months.

- [Ryan] So you have people hanging over the side

of these lifeboas, waiting to be rescued.

Now during this journey,

one of the men on the boat says they were attacked.

There were tentacles coming out of the water,

wrapping around people, injuring them,

or pulling them back into the ocean.

He says, "I was attacked as well,"

and he actually watched an Indian servant be pulled down

with these thick tentacles and devoured.

- This sounds like a tall tale,

but 15 years later,

the eyewitness shows the circular scars on his leg

to a marine naturalist,

who confirms that it was caused by the suckers

of an animal more than 20 feet long, just like the Kraken.

- [Laurence] More than a thousand years

after it first appears in written records,

the Kraken remains a mystery.

What could this terrifying monster really be?

- The thing that the Kraken is most known for

is its massive tentacles.

And there are animals in the sea today

that have tentacles, and they're called cephalopods.

- [Lynne] Typical kinds of cephalopods in the ocean

are just not nearly on the scale of the Kraken,

and in fact, there's really only one potential sea creature

that would even come close to that size.

[tense music]

In the 1850s, a Danish zoologist

by the name of Japetus Steenstrup

is gathering information about these different types

of documented giant creatures,

one of which is the sea monk, which is this large creature

purportedly resembling a monk or a friar,

and these red, flowing robes

that sort of hang in sheets off of his body.

- And as he continued to look at these accounts,

he came up with a scientific description of this monster,

which he called Architeuthis Dux, the giant squid.

This is the first time

where we have a scientist formalizing a description

based on these historical accounts of the Kraken.

- [Laurence] Later in the 1800s,

evidence supporting his theory begins to emerge.

- [Peter] In 1875 in St. John's Newfoundland,

there is an attack of a small boat by a giant squid.

And what's really stunning

isn't just the description of the attack,

but that the sailors, in an effort to save themselves,

grabbed an ax and hacked off a limb.

- The creature slides off into the water and disappears,

but now they have evidence.

One of the tentacles that they have in their boat

is 19 feet long.

- If you were a sailor

and you didn't know the proportions,

you could easily imagine that this was only a tiny fragment

of an even more massive beast.

- Around the time of this encounter in 1875,

full giant squid carcasses

begin washing up off the shores of Newfoundland.

This is the first time that zoologists have an opportunity

to study an intact giant squid.

It features a body which is also called a mantle,

eight shorter arms, two very long feeding tentacles,

and what might be the most fearsome part of this creature,

its mouth or beak.

- By the early 1900s, the scientific community

finally has to admit that Steenstrup was right,

that there is a giant sea beast at the bottom of the ocean

that could be the Kraken that everybody's talking about.

- [Laurence] Unfortunately, live giant squid

prove to be elusive creatures.

Decade after decade goes by without any sightings.

- It's not until 2004 that a living giant squid

is spotted in its natural habitat,

and this happens about 600 miles off the coast of Tokyo.

A marine team has been tracking

what they believe to be a giant squid

using a baited line to try to lure it to the surface,

and on their hundredth dive,

they finally capture it on camera.

- [Ashley] And now, because it's 2004,

we're not talking about the world

of ancient mariners in Denmark

writing letters to each other.

This became a worldwide sensation.

- The world has the first image of a living giant squid.

And watching the animal in its natural environment

answers at least some questions about the Kraken legend.

First of all, the creature's deep-sea habitat

helps explain why encounters with it

have been extremely rare

and the power of its large black beak,

now seen in action by scientists,

jives with descriptions of the flesh-eating monster.

- [Ashley] That beak, which of course has evolved

for catching prey in the deep sea,

is strong enough to sever a steel cable.

- [Laurence] The question remains

whether giant squid grow large enough

to take down ships or devour humans,

as in the Kraken legends.

- [Peter] The squid that was seen off the coast of Japan

was a juvenile,

and while it gave us a sense

of what these squid looked like when they're swimming

and how they position themselves,

there's still a lot that we do not know about the adults.

- If the complete length of a giant squid

is something like 50, 60 feet,

compared to even the largest things in the ocean,

in terms of length and almost in terms of weight,

these are truly large animals.

- [Laurence] But is it possible

for giant squid to grow much larger,

to mammoth sizes we've yet to document?

Some marine biologists say yes.

- There has been this idea of deep sea gigantism

that sometimes at deep depths in the ocean,

things are able to achieve a larger size

than they do at more shallow depths.

- Scientists have studied this phenomenon for decades

and we know that as we look at creatures

that live in the deep dark ocean,

some of them reach extraordinary sizes

because it helps them get around the deep sea

and find what little food there is.

- One reason that we postulate

that the giant squid don't come to the surface very often

is because the amount of energy it would take

to rise up from those deep, cold depths

would be too much of a caloric intake.

- These creatures are certainly not going

to be comfortable living at a higher level,

so it makes sense

that sightings would be incredibly rare.

- [Peter] We know that there are giant squid

that are close to 60 feet,

but could they actually get to be

but could they actually get to be

100 feet, 120 feet?

We don't yet have the answers,

but I think the more we look, the more likely we're going

to encounter these giant creatures lurking in the deep.

- For centuries, sailors in and around Scandinavia

talk about deadly encounters with a Kraken,

a sea creature some experts believe matches the giant squid.

But is that the only possibility?

- Some stories of the Kraken actually have features

that don't match well with the features of cephalopods.

Some have enormous size but are relatively flat in shape,

and it leads us to ask the question,

what other things might have been referred to as the Kraken?

- In 1765, one sailor describes seeing a Kraken

as an enormous fish, but with tiny eyes and fins,

so we're not always talking

about something that can be explained

by the existence of the giant squid.

And some scholars have actually suggested that it might instead

share more characteristics

with a different type of marine animal.

[tense music]

- Whales are enormous

and it's hard to fathom how big they are

until you're alongside them.

When those whales feed, it's loud and boisterous

and it is a sight to behold.

And the cool waters of Scandinavia

are home to many whales

because that's where their food is.

- These whales existing in that environment

tend to be a little bit larger.

I mean, you have humpback whales at almost 60 feet.

You have sperm whales, almost 70 feet.

You can see how these sea animals

could inspire the Kraken mythology.

- Whales are the largest creatures that have ever lived.

Imagine that you're out at sea

and something strange rolls across the surface

and all you see is a dinner-plate-sized eyeball.

That looks like a sea monster to you.

- So there's a real instinctive fear

simply encountering that size of creature,

who, for the most part, is really not interested in us.

But there was one instance off the coast of Ecuador in 1820

when the whaling ship, the Essex, was attacked by a whale

that it had been attempting to harpoon,

and the whale rammed into

the side of the ship and split it into two.

- The story of the Essex was widely reported

after the few survivors came to shore

and was a major influence, we believe,

in Herman Melville's writing of "Moby-Dick."

- After the destruction of the Essex,

that kind of helped stir the lure of giant sea creatures

that are powerful enough

and mean enough to take out an entire ship.

- [Laurence] In 2024, a much smaller fishing boat

off the coast of New Hampshire

is slammed by a breaching sperm whale.

- The sperm whale body checked a small boat.

The whale didn't pursue the boat

or try to damage it any further.

I think it probably was just as confused as the sailors.

- Nobody dies in this case, thankfully.

The ship is flipped, the people take a dive off of it

and are rescued by two other fishermen.

- [Laurence] There is one whale species so enormous

that any encounter could easily destroy a fishing boat

and kill everyone on board.

- Blue whales are unbelievably huge organisms.

They can grow to over 100 feet long

and weigh more than 200 tons.

To put that in perspective,

the largest dinosaurs ever weighed about 65 tons.

- If you had not yet seen a whale,

or even if you had seen a whale and not seen a blue whale,

the scale difference there

is enough to really make you question what you had seen.

- Even though blue whales feed on krill,

which, tiny little marine animals,

the odds of them swallowing a human

or going after humans is almost zero.

But somebody could have just happened

to be in the wrong place at the wrong time

and, boom, swallowed completely.

- [Laurence] It's hard to imagine

this happening in real life,

until a marine biologist claims he was swallowed by a whale

and has the pictures to prove it.

- [Ashley] In 2019, Rainer Schimpf was taking photos

on the coast of South Africa

when he was swallowed by a massive whale.

He spent about 30 seconds in the mouth of this whale

before being spit back out, but he made it through unharmed.

- No one would've ever believed him.

It would've been just a big fish tale

if it wasn't for his wife,

who was standing nearby

and snapping photos of the whole incident.

- If that story weren't enough,

we have further accounts.

In 2025, off the coast of Chile,

a man kayaking is caught on camera

in the moment that a whale rises up from beneath him

and scoops him up entirely.

- He was quickly spat back out

because whales do not eat people.

But if you're in the wrong spot,

even if you're in something as large as a kayak,

you might get swallowed by a whale.

- Even if these encounters with whales

that led to them being engulfed are harmless,

witnessing or experiencing something like that

could easily contribute

to the myth of the man-eating Kraken.

- [Laurence] Is it possible a whale

might be mistaken for a Kraken,

not just at sea, but on dry land as well?

- Unless you understand anatomy,

if you encounter a decomposing animal,

particularly a sea creature on the beach

that's getting reworked by the elements,

it might be very hard to identify what that creature is.

- In 2017, a strange, misshapen carcass

washes up off the shores of the Indonesian island, Seram.

Photos of it

immediately go viral worldwide.

It's 50-feet long, bloated,

and unlike anything that's ever been seen before,

- People are talking about weird fur on it

and that there's this red liquid nearby

and they're just baffled.

So it's easy to understand how they could have thought,

"This is the Kraken."

- Many cases of unexplained animals

or unexplained carcasses

have very poor quality documentation,

but eventual testing of this revealed from DNA

that it actually was part of a baleen whale.

What was initially thought to be fur

was actually the structures within the whale's skin

as it falls apart.

The red fluid was eventually identified as whale blood.

- [Laurence] For centuries, people have been searching

for evidence of the giant sea monster known as the Kraken.

Marine biologists have compared it

to whales and giant squid,

but neither seems to be a perfect match.

- What if there is something else out there,

an unknown sea animal that

we just haven't been able to capture yet?

- Scientists pretty much dismiss this idea

that it could be its entirely unique species

until a group of fishermen in the 1970s

haul in something truly unexpected.

- In 1977, a Japanese fishing trawler

was able to pull in this massive carcass.

This thing was 30 feet long and 4,000 pounds.

- This is truly something they have never seen before

and cannot account for.

It appears to have an incredibly long backbone.

It has these four sort of strange fins on it,

but because it smells so atrocious,

they all decide to toss it back in the ocean.

- Luckily, somebody snapped a couple of photos of it

and actually took a sample,

and they sent that sample away to get it tested.

Now what's interesting is,

normally a sample comes back

and you're like, "Oh, blue whale."

This came back inconclusive .

- Based on photos, based on the description

that the fishermen were able to give,

the official interpretation that the government makes

is that this was likely a decomposing basking shark,

so it's one of the largest creatures there is.

They grow up to about 30 feet long.

- [Laurence] But another Japanese scientist

has a much more controversial theory.

- Professor Tokio Shikama of Yokohama National University

believes that the carcass

is actually the remains of a dinosaur,

specifically the plesiosaur,

which was one of the deadliest beasts to ever roam the seas.

Some descriptions of the Kraken

do fit with certain aspects of the plesiosaur.

So if the dinosaur had managed to survive to modern times,

as Shikama maintains,

that would mean that the origin of the Kraken

actually goes back millions of years.

[tense music]

- Plesiosaurs are large, aquatic reptiles

that lived during the time of the dinosaurs.

They lived in the Cretaceous Period.

- These creatures are the T. rex's of the ocean,

big giant animals with extraordinary teeth

that were voracious hunters.

And they've been extinct for some time.

But this professor said,

"Well, this could well be a plesiosaur

that we just have never caught before."

- [Laurence] If this creature is a survivor

from the age of dinosaurs, then it rewrites everything

we thought we knew about their demise.

- Most scientists agree that

there was a mass extinction event

about 66 million years ago

when this asteroid, six to nine miles wide,

slams into the Yucatan Peninsula with such power

that it drives itself 14 miles into the Earth.

- When you have an asteroid that is this size,

you have boiling oceans,

you have pure darkness that takes place,

and also displacement of a lot of water,

so it wiped out 75% of the Earth's species.

And for the animals that dwell in the water,

this was the apocalypse.

- [Laurence] Yet some theorists counter

that an asteroid strike in the Yucatan,

no matter how destructive,

wouldn't wipe out all the dinosaurs around the world.

Some, they contend, could survive the cataclysm.

- The Loch Ness Monster is arguably the most famous

possible plesiosaur in the world,

and Loch Ness is connected to the ocean,

but so far away that you could theorize

that if they were inland when this happened,

they would've been saved from this catastrophe.

- [Kavitha] It's interesting to note

that Loch Ness does connect to the open ocean,

the North Sea, which then connects to the sea of Norway,

and all of these waters surround Scandinavia.

- [Ryan] The Loch Ness Monster has gathered

decades of attention, but until they find a body,

there is no way to prove

that the Loch Ness Monster or a plesiosaur

is what is actually the Kraken.

- [Laurence] There are other formidable predators

thought to be long extinct

that share similarities with the Kraken.

One is a giant fish

that cruised the seas for a million years.

- There are some Kraken descriptions

that talk about a long, sleek fish with massive teeth,

and this has led many to think that maybe,

that's evidence that megalodon still lives.

[tense music]

- [Ryan] We have great white sharks

which can grow up to about 20 feet in length,

and the megalodon was two times the size of the great white

or maybe bigger,

the largest fish ever to exist.

- [Lynne] It is believed to have gone extinct

about 3.6 million years ago,

but of course, similar to the plesiosaur,

there could have been

some that survived down in deeper water,

still living in the oceans today.

- Most scientists think this is highly unlikely

because no bones or teeth of a megalodon

have ever been found on the ocean floor

that weren't fossilized.

But some theorists wonder if maybe a few megalodons

actually did manage to survive into the modern era.

- [Laurence] It might seem farfetched,

but there are other examples

of prehistoric beasts surviving the asteroid impact

that have been verified by scientists.

- [Ryan] In 1938, a South African fisherman catches

something that he's never seen before.

It has these armored, blue scales

and its fins aren't normal like fish fins.

They're actually fleshy.

- So he sends this off to a marine biologist

who absolutely cannot believe what she's seeing.

It's called the coelacanth,

but the most recent one was from 66 million years ago.

- The news of this is so startling, it's a bizarre animal

and maybe one people hadn't thought of before,

but the resurrection story of it

led to a worldwide recognition of an animal

that was thought to be from the age of the dinosaurs.

- [Laurence] Evolutionary biologists

are faced with a new mystery:

If this prehistoric fish survived the great extinction,

is it possible a beast like the Kraken did as well?

- Perhaps the coelacanth fish survived

because it's relatively small.

It's only six feet long

and weighs about 200 pounds,

so it doesn't require a ton of food.

But for a species the size of the Kraken

to endure an extinction event,

it would've had to have somehow been protected

from all the destruction.

Some wonder if maybe there were sealed pockets

in the ocean floor that acted as safe zones

for colossal prehistoric beasts,

and something later happened to open these pockets

and something later happened to open these pockets

to release one of these beasts into the ocean.

- Could the Kraken be more than a mariner's myth?

Scientists are still trying to find out

whether or not this infamous sea creature is real.

If it is, could it be a survivor from prehistoric times,

something that could grow three stories tall

and crush the skeleton of even the largest predator?

- In 2011, at a meeting of the Geological Society of America,

paleontologist Mark McMenamin presents

a really interesting and controversial idea.

- He says, "I have found something that I believe

is proof that the Kraken is a real beast

and did exist about 200 million years ago."

He was unearthing fossils

in a ghost town called Berlin in Nevada,

and he came across an ichthyosaur,

which we know existed.

- These are almost dolphin-like in shape,

many sharp, pointed teeth in a long snout,

very highly adapted to ocean life,

and the fossils that were found in Nevada

are actually whale-sized.

- What's strange to McMenamin

isn't the existence of the ichthyosaur,

but that when he finds these bones,

he doesn't find just one set.

He finds nine of them, and they're all arranged

in a distinct pattern.

These piles are not the result of nature.

Some other creature had to have placed them there.

- [Lynne] The ichthyosaur would've existed

near the surface of the ocean.

Of course, this is a time

when Nevada was entirely underwater,

so whatever killed them

traveled to the surface of the water,

hunted them, and then brought them down, all the way

to the floor of the ocean to stack their bones.

- If you then take the markings

on the actual bones themselves,

they don't look like teeth marks.

They look like something that a beak would do.

And to pull something of that size down into the depths

and hold it down and eat it,

you would have to be enormous.

So he postulates that this is an ancient giant cephalopod.

- McMenamin is convinced and he keeps digging,

and he finds what he thinks is the jackpot:

a beak, the kind of beak that would have come

from a creature about 100 feet long.

- [Laurence] The giant squid is not the only creature

that uses a beak to tear apart its prey.

In this case, the evidence points more toward an octopus.

- [Ryan] What we know about octopus

is they attack with twin beaks

and they pile the bones of their victims

in front of their lairs.

You know, they use this.

These are traits we know and we have witnessed in nature.

- Today, the largest octopus that we have is

a lot smaller than the largest giant squid that we have,

but it's entirely possible that in the prehistoric eras,

there was an enormous octopus species

that could have survived into modern day

and become what people saw and called the Kraken.

[tense music]

- [Kavitha] During the great extinction,

earthquakes caused massive craters

on the sea floor some many miles deep.

Some species, including octopus, which prefer to live

on the sea floor in spaces like these,

could have found sanctuary in them

and survived the apocalypse happening above.

- Imagine if you had the size, the stealth,

and the intelligence to hunt and stay unnoticed

by not only the predators in the sea,

but the predators from above.

And the one thing we know about octopus

is that they are arguably

the most intelligent species in the entire ocean.

- We know very little about what lives on the sea floor.

You'll hear people say that, you know,

we know the surface of Mars

better than we know the floor of our own ocean,

and that is literally true.

- In 2024 in Norway, scientists have been

discovering these sites called hydrothermal vents

on the sea floor that are just booming with life.

A secret to success are the bacteria

that are able to take the chemicals

that come out of there, really noxious chemicals,

and to eat and to grow off of it, and you end up

with these really lush communities of creatures

all basically living off the energy

that comes out of the inside of the Earth.

- This totally changed the way that we thought about

the domains in which life could exist.

The animals at these deep sea vents

don't necessarily even need sunlight.

If the sun blinked out, the animals at the deep sea

might not know about it for millions of years.

- [Kavitha] Many marine biologists dismiss the theory

of the Kraken emerging

from these deep sea holes

as something out of a Jules Verne novel.

Just because a giant prehistoric cephalopod

might have existed many millions of years ago

doesn't necessarily mean that it survived

into the days of seafaring humans.

- [Laurence] But others say it's not so far fetched.

It's estimated that 2/3rds

of the marine species in our oceans

have yet to be discovered,

and some argue that among them

could be survivors of the great extinction.

- Every time we go exploring in the deep sea,

we find creatures that we had not previously known,

and some of them are big/

So are there monsters lurking in the deep

that we don't know about?

It's possible.

- [Laurence] For centuries, people have been trying

to identify the Kraken

by comparing it to other marine life, real or imagined.

Now, some are asking

if other factors fueled the imaginations of sailors,

especially those heading into the treacherous waters

of the Scandinavian seas.

- One of the descriptions of a Kraken attack

is that suddenly the ocean begins to spin

and it creates this massive whirlpool

that sucks ships down to their graves.

- The churning waters off the coast of Norway do just that.

Their force inspires writers like Edgar Allen Poe,

who wrote a short story about a man who survives a shipwreck

and a whirlpool that he calls a "maelstrom."

- The legends of the maelstroms could well be based in fact.

The Saltstraumen Channel on the Norwegian coast

has terrifying opposing tidal currents.

They can capsize boats, and when that happens,

people can drown and people have drowned there.

It's taken many lives.

- Sailors back then, all they saw was rapidly moving water,

a vortex that was being created and getting bigger.

You might perceive that as a beast

because they didn't know what we know now.

- [Laurence] Could it be that generations of sailors

have been blaming ship disasters

on an imaginary creature, when the sea itself is to blame?

[tense music]

- Most long-lasting maelstroms are not the consequence,

like a tornado, of wind masses,

but actually of convergent currents in the ocean itself

that when they meet at different angles, produce a vortex.

- [Karlene] These vortexes that are being created,

they're moving at a pace of about 23 miles per hour.

They could be about 33 feet in diameter,

and that creates the illusion.

Not only are you out there thinking about a mythical beast,

but you're also seeing some movement in the water.

- [Laurence] It's rare that these whirlpools

are strong enough to pull in entire boats,

unless the circumstances are just right.

- Maelstroms are especially dangerous

when they have a deep hole at the bottom of the water

that acts like a drain speeding up the flow.

- One incredible example of this

is something that happened in 1980

in Louisiana's Lake Peigneur.

In this lake, there's two activities going on.

One is a salt mine being dug out underneath the lake,

and one is an oil rig.

And due to an accident of calculations,

they end up drilling

into one of the lower shafts of the salt mine.

- And as they're drilling, they hear a couple of loud noises

and then the water begins to spin around the rig.

The lake is only 10-feet deep,

but what happens is they created

the hole needed for the water to go into the salt mine,

multiple levels, thousands of feet down.

In seconds, it sucks a tugboat, 11 barges,

an entire island with a botanical garden on it,

into the whirlpool, gone.

Maybe the most incredible thing about it

is that nobody was hurt.

- That was human error.

You're talking about an oil rig

that went right into a salt mine.

That's something that definitely

does not happen every single day,

but we also see these whirlpools

that are created out in the open water

just from naturally occurring events like earthquakes.

- [Lynne] In 2004, off the coast of Thailand,

an underwater earthquake caused a tsunami so large

that the loss of life topped 200,000 people.

And in 2011 in Japan,

a similar tsunami took out 19,000 people

and the entire Fukushima Nuclear Plant.

- In both instances, the first to succumb

are people sailing near the quake's epicenter.

Before a tsunami rises up from the displaced tectonic plates

and hits the coast, there are several moments

when water fills inside the enormous cavity,

and in that case, boats as far as 10 miles out

can be sucked into this giant whirlpool

that's been created by the cracks in the sea floor.

- [Laurence] In such events,

it's possible sailors might have confused

a natural maelstrom with the Kraken's attack.

- You have to ask,

how many times could this mistake have been made?

How many times could someone have seen

a natural phenomenon like this

and attributed it to this monster?

- [Karlene] If you're already going out there

with the notion that there is a beast in the water

and you continue to see the whirlpool getting bigger,

you're gonna think that the beast is

about to jump out of that wate,

and you're about to be face to face with the Kraken.

- [Laurence] Many theorists have turned away

from trying to link the Kraken to a living creature.

Some now wonder if

the psychological effects of sea travel

gave rise to this legendary beast.

- You have to think about the conditions that

sailors live with, especially hundreds of years ago.

A lot of sailing voyages

could be up to three years at a time,

and with that much isolation and open ocean,

you can imagine that sailors

would start to lose their grip on reality.

- We walk on land, we live on land.

To remove you from that

is something that you have to experience to understand.

It begins to immediately play with your mind.

- Some experts have theorized

that the stories that are told about the Kraken

aren't the result of any actual creature in the ocean,

but instead are a sign of the psychological impact

that being on the ocean has on the crew.

[tense music]

- You can imagine how terrifying it is

to go to sea in an old, rickety sailing ship

with no GPS, no weather forecast,

and you probably don't have much of an education,

certainly not in zoology.

- Many sailors in the past couldn't even swim,

and so anything that happened

beyond the bulkheads of a ship

was often misunderstood.

- These sailors are dealing with stress and storms,

cabin fever, and obviously heavy drinking,

and all of these things can actually affect

whole crews at the same time.

It's called mass hysteria,

a phenomenon where a group of people

can experience similar physical or psychological symptoms

without a singular, identifiable medical cause.

- In 2024, the U.S. Navy did a really interesting study

and found that 41% of sailors going to sea

suffer a form of high stress before getting on the boat.

Let's go back hundreds of years ago

and you're about to head off into sea,

and the only thing you know is that there is

a Kraken out there waiting for you.

Tell me that your stress levels wouldn't be through the roof.

So these sailors weren't just battling sea monsters

and crazy environmental problems,

they were also battling themselves.

- [Laurence] Diseases at sea can also induce hallucinations.

- Another big component back then was scurvy.

And so scurvy is a lack of vitamin C,

and that deficiency is a horrible way to go.

You're talking about your arms

as well as your legs being sore and then stiff,

you have your teeth falling out, your gums are bleeding,

and then eventually it makes its way into your brain

and causes damage.

- Under the stresses of scurvy,

sometimes the senses become changed,

and in the 1740s, an entire squadron

of British sailing vessels was overcome with scurvy

and their sailors reported strange sounds,

exaggerated sights, and one famous report

was of a man who the simple smell of a flower

was enough to make him scream in agony.

- According to one historian,

scurvy is responsible for more deaths at sea

than storms, shipwrecks, and other diseases combined.

And it was not a quick death.

It could take weeks for people to die of scurvy.

- You're in this mental state because of scurvy,

your brain is deteriorating,

so what you think you saw

might not actually be what is out there.

- [Laurence] Hallucination brought on by

psychological stress, fear, and disease

might be a convincing explanation

for stories of the Kraken,

but it's not the only way the brain might trick us

into believing there are strange creatures nearby.

- For folks who spend time at sea,

you realize very quickly that your eyes can deceive you.

The fact that you don't have a frame of reference

when you look out across the ocean

means that things can seem grander

and larger than they appear.

[tense music]

- [Karlene] Atmospheric factors play into this.

You have the cold air that's closer towards the sea level,

the warm air that's rising over it.

Once that light moves from cold air into warm air, it bends,

and so that changes

what you are physically seeing out in the distance.

The flying mirage illusion

can make it look like a boat is in the air

because of the way that the light is bending,

so your perception is off,

and that creates a bigger story

when it comes to creatures

that are out there on the open water.

- Even real objects perceived

with these atmospheric conditions

can be elongated, stretched, or bent

in ways that might make them appear monstrous.

- [Laurence] Could phenomena like these

have contributed to Kraken sightings?

- At the end of the day, the oceans are not our home.

That is not our natural environment.

So I don't care how brave you are

or how prepared you are, you're going to step off

into that adventure with a little bit of apprehension.

- Stories of the Kraken have been around for centuries,

and even modern discoveries

don't fully explain where they came from.

- [Peter] History is replete with stories

of sailors talking about creatures trying to kill them,

and if you take a look at them,

you begin to see that those monsters

probably tell us more about us than anything else.

- It may be tempting to dismiss the Kraken

as the world's oldest maritime legend,

or the product of sailors' minds playing tricks on them.

But if so, then why does the Kraken still fill us

with fascination and fear?

With as much as 80% of the ocean still unexplored,

discovering a sea monster

that truly lives up to the Kraken lore

may just be a matter of time.

I'm Laurence Fishburne.

Thank you for watching History's Greatest Mysteries.

[dramatic music]