Original subtitles

Tonight, the world's most enduring

deep-sea monster mystery.

I saw the head, the neck, and the huge body

which I'd say was about 30 feet long.

HEIDI HOLLIS: We are talking about thousands of sightings,

and that's a conservative estimate.

It could be tens of thousands over the course of 1,500 years.

Despite so many sightings, the beast remains unidentified.

There are millions of species

that we haven't found or classified yet.

There's stuff out there that we don't know anything about.

As far as we can tell,

nobody has ever captured a Loch Ness Monster.

Now, we'll explore the top theories

surrounding this elusive creature.

Hey, maybe it's a plesiosaur.

KRISTYN PLANCARTE: What about the thing that washed up

in Stronsay, or the similar lake monster in Sweden?

JONATHAN BIRD: There are tons of eels in Loch Ness.

Is it possible that there is a gigantic eel?

DUSTIN GROWICK: Many people still believe it's real.

Does the Loch Ness Monster exist?

And if so, what is it?

[music]

LAURENCE: Northern Scotland, August, 564 A.D.

According to legend, an Irish monk named Columba

is attempting to cross the River Ness with a group

when they stumble upon two men burying a friend.

This man had just been swimming when he was attacked

by an enormous water beast.

DUSTIN: You would think that after that exchange

the monks would try to find a different river crossing.

But Columba stays, undeterred.

Maybe he didn't believe the locals,

or he just thought that his faith will protect him.

ZAK MARTELLUCCI: He orders another monk

to swim across and retrieve a small boat.

As this monk gets about halfway across,

this creature suddenly appears out of the water,

gives a giant, bellowing roar.

LAURENCE: Everyone panics, with the exception of Columba.

He steps right up to the edge of the bank,

makes the sign of the cross, and demands the monster

leave the man alone.

LAURENCE: The creature supposedly obeys.

To the witnesses on shore,

it is nothing short of a miracle.

KAREN: Columba eventually achieves sainthood,

and this tale is supporting evidence

for his faith and abilities.

And this story is retold for years to come.

LAURENCE: Debate continues for centuries.

What could this mysterious creature actually be?

In Columba's time, and continuing

for several centuries after, through the Middle Ages,

dragons are still believed to be real.

And so, many people think this is some sort of sea dragon.

But nobody has any concrete evidence of what it is,

or if it even truly exists.

It remains an essentially local legend

for quite some time.

LAURENCE: Then, in the 20th century,

new visitors flock to the Highlands,

thanks to one remarkable invention--

the automobile.

By the early 1930s, there's a road built

along the shore of Loch Ness.

HEIDI: One afternoon in 1931,

a local couple were driving along there

when they spotted a large animal.

It was rolling and plunging on the surface of Loch Ness.

Immediately they report their experience

to the local papers.

When published, their story

uses the now-famous key word, "monster."

LAURENCE: The Loch Ness Monster--

a name that soon spreads far and wide.

HEIDI: Now all of a sudden,

the tourists are not coming

to see the beautiful lake and the rolling hills.

They are coming to see the monster,

who is soon lovingly called "Nessie."

And guess what? They are spotting it, all right.

They are spotting it in droves.

LAURENCE: Soon, there are more eyewitness accounts of Nessie,

and they seem convincing.

I saw a-- a large object.

It came right out of the water in front of me.

I was wading in the river fishing with-- fly-fishing.

The best view I ever had was the very first in 1934.

I saw the head, the neck, and the huge body

which I'd say was about 30 feet long.

LAURENCE: Each new glimpse brings fresh seekers,

all with the latest technology.

ZAK: We shouldn't have to wait long

before somebody captures it on film,

and then we're bound to know what it is.

LAURENCE: In April of 1934, that finally happens,

and it becomes front page news.

A gynecologist from London named Robert Kenneth Wilson

went on a fishing trip over there to Northern Scotland

when he decided to go for a walk.

During his stroll, that's when he spotted something

unusual in the water.

Luckily, he had his camera, and he snapped a picture.

And there we have it,

probably the first photograph of Nessie.

LAURENCE: Known as "the surgeon's photo,"

the image causes quite a stir.

KAREN: Shows a silhouetted creature

with a long, slender neck, a small head,

and a large body emerging slightly above the waterline.

DUSTIN: This is amazing.

We finally have some visual evidence

to back up these eyewitness accounts.

And not only that, some experts

think they can identify this animal.

LAURENCE: The creature's shape also strikes a chord

with British paleontologists.

So, what particular species do you think it is?

The evidence as I interpret it all fits--

and I know this is a fantastic statement--

but this all fits plesiosaur.

LAURENCE: Plesiosaurs are a marine reptile

dating back millions of years.

Their fossils were first discovered in 1823

during a dig in England.

HEIDI: Fossil hunter Mary Anning actually uncovered

a nearly complete skeleton of a previously unknown species.

It is given the name Plesiosaurus,

meaning "near to reptile."

Plesiosaur fossils have been found around the world,

but a major cluster of them comes from here in Scotland.

We're talking about hundreds of specimens.

This was, at least at one time, this creature's main habitat.

KAREN: These fossils show that the plesiosaur

was an enormous water-dwelling creature,

over 20 feet long.

They had broad, flat bodies with short tails.

Their limbs had evolved into four long flippers

that propelled them through the water in a flying motion.

HEIDI: They breathe air, and so they would constantly

have to come to the surface for oxygen.

Most notably, they had long thin necks.

The surgeon's photograph happens to fit that to a T.

And coincidentally, so do most of the witness statements.

LAURENCE: Though some believe Nessie could be a plesiosaur,

the theory has one major flaw.

DUSTIN: Scientists believe that a mass extinction event

about 65 and a half million years ago

killed about 75% of all species on Earth,

including dinosaurs and plesiosaurs.

A plesiosaur should not be inhabiting these waters today,

in Saint Columba's time,

or any time during human existence.

They're supposed to be extinct.

LAURENCE: But is it possible the plesiosaur somehow survived?

When we say that 75% of the creatures

did not survive the last mass extinction event,

that means that 25% did survive.

So, platypuses, turtles, crocodiles--

all kinds of animals actually did survive that event.

LAURENCE: Scientists point to a fish

long thought to be extinct as an example--

the coelacanth, discovered alive in 1938

in South Africa.

KAREN: The entire scientific community believes

that the coelacanth dies off 66 million years ago.

There are no fossils after that.

It's the same time as the plesiosaur.

If the coelacanth can still be swimming around out there,

what's to say that a small number of plesiosaurs

couldn't have somehow avoided extinction, too?

LAURENCE: But to many, the plesiosaur theory

remains too far-fetched.

DUSTIN: The fact that they breathe air

could account for the animal being sighted at the surface,

but I actually think that's evidence

against Nessie being a plesiosaur,

'cause it would have to surface all the time.

If that were the case, we'd have so many more photos and videos.

One would have probably already been caught

and put in a zoo by now.

Plus a creature as big as a 20-foot-long plesiosaurus

would need a lot of food to sustain itself.

ZAK: There's just not enough of a food source

for a massive beast, let alone a community of them,

which there would have to be in order for this species

to survive this long.

HEIDI: And honestly, the plesiosaur theory

only hangs on the one photograph.

And before the surgeon's photo is published,

absolutely nobody thinks it's a plesiosaur.

LAURENE: 1934-- the first photo

of the supposed Loch Ness Monster

incites public frenzy and a torrent of tourists

looking for Nessie.

But not everyone believes the image

known as "the surgeon's photo" is authentic.

DUSTIN: Dr. R. Kenneth Wilson, who submits this photo

to the Daily Mail, claims that it's real,

but others say "Hold on, this is an elephant's trunk

"rising out of the water, or maybe it's a dolphin's fin,

or something else."

KAREN: What we do know is that the photo that's published

is substantially cropped and zoomed in,

which blurs the shape of the creature a bit

and skews any sense of scale or perspective.

But when some experts go back and examine

the original, uncropped photo,

they see something entirely different.

Seeing the uncropped version

changes their perspective completely.

They believe that whatever this beast is in the water

isn't anywhere near 20 feet long.

It's maybe three feet long, at the most.

LAURENCE: Is it possible that the most famous photo of Nessie

is somehow doctored?

HEIDI: People question the authenticity

the moment this photo comes out in 1934.

But many people still believe this thing is real.

And there is no definitive proof otherwise.

Then, in 1994, the photo's whole provenance

comes into question, thanks to a deathbed confession

by a man named Christian Spurling.

He claims that in 1933, his stepfather was hired

by the Daily Mail to find evidence

of the Loch Ness Monster.

Spurling is the stepson of a big-game hunter

and filmmaker named Marmaduke "Duke" Wetherell.

KAREN: So, Duke goes on this expedition to Scotland,

and it doesn't take him long to find

these really large animal tracks near the banks of the loch.

Judging from the size of the footprints,

Duke estimates the animal to be at least 20 feet long.

LAURENCE: Wetherell sends plaster casts of the tracks

to a London museum.

When the results came back, they find that the tracks

didn't come from a monster, but they came from a hippo.

It sounds unusual because we all know

that hippos do not come from that area.

But back then, hippo's feet were used as umbrella holders

and ashtrays, so it wasn't that uncommon.

DUSTIN: So, one of two things is happening here.

Either Duke faked the tracks, or someone was fooling him.

The Daily Mail is not happy about either of these options,

so the paper publicly ridicules him.

LAURENCE: According to Spurling's confession,

Wetherell concocts a scheme to save his reputation.

Duke goes to his stepson, who happens to be a model-maker,

and asks him to fabricate something

that looks like the eyewitness descriptions of the beast.

So, using plastic, wood, and a toy submarine,

they create this model of a creature

with a long neck and small head.

HEIDI: And then, Duke goes to the loch with his other son

and creates that iconic photograph.

But in reality, it's just a picture of the model

floating in the water.

LAURENCE: Now, Wetherell just needs a way

to make the photo public.

The perfect solution?

The surgeon, Dr. R. Kenneth Wilson.

Duke realizes the best way he can pull this off

is if he finds someone trustworthy

who can claim the photo as their own.

So, he passes the photo on to Wilson,

the very same surgeon who publicizes the infamous photo.

HEIDI: The surgeon's photo is really a game-changer.

It unleashes a torrent of tourism

that still is going on to this day.

LAURENCE: Over the years, there are more fake photos of Nessie,

all of them eventually debunked.

Then, in 2016, there's suddenly new evidence

that suggests the monster could be real.

DUSTIN: Researchers from Kongsberg Maritime

send an underwater drone deep into the loch

to search for any evidence of the monster.

And surprisingly, the sonar returns images

of something that has the shape of the monster's head and neck.

At first, this is big news.

LAURENCE: Until it's determined to be a prop from a movie.

DUSTIN: In 1969, a Sherlock Holmes movie

was shot at the loch.

In the movie, there's a scene where the Loch Ness Monster

attacks the heroes.

But during the filming, director Billy Wilder

takes a look at the monster prop

and decides he does not like the humps on the back.

So, they remove the humps, and accidentally cause the prop

to sink to the bottom of the loch.

HEIDI: There's a lot of fakery

surrounding the Loch Ness Monster.

People love getting their 15 minutes of fame from this.

Every Nessie sighting gets attention,

and people love getting attention.

LAURENCE: But the sheer volume of sightings throughout time

convince many that Nessie is real.

We are talking about thousands of sightings,

and that's a conservative estimate.

It could be tens of thousands, over the course of 1,500 years.

DUSTIN: Before cameras, before Photoshop,

before robotic toy submarines.

Sure, a few dozen sightings may be fake.

But all of them?

[clicks tongue] No way.

LAURENCE: A key piece of evidence for believers--

a discovery in 1808 on the Scottish island of Stronsay,

just 120 miles from Loch Ness.

According to eyewitnesses, the corpse of a strange animal

washes up on the beach and a crowd gathers to see it.

It's the rotting carcass of an enormous,

unidentified sea beast, and the locals

have never seen anything like this.

Eyewitnesses call it the "Stronsay Beast,"

and describe it as having a serpentine-like body

with a long neck and six limbs that resemble paws.

They say its head is small like a sheep's,

and its eyes are similar to a seal's, but bigger.

It has some short hairs around its head and neck,

and skin that is rough to the touch

and grayish in color.

ZAK: The measurements they take show how gigantic

this thing actually is.

It's 55 feet long, with its neck alone

measuring 10 feet.

LAURENCE: Authorities document the creature

and take sworn witness statements.

This is the early 19th century, so they can't photograph it.

But they also know the story won't be believed,

so they need to prove it somehow.

So, they bring all the eyewitnesses

to the capital where they can swear before a magistrate

that what they saw is the truth.

We still have these records,

along with drawings that they made.

KAREN: The carcass is quickly decomposing,

and they lack the right equipment to transport

or preserve this massive animal,

but they do take samples of the specimen.

The skull is saved and sent to London

for further examination, but unfortunately,

it is destroyed during the Blitz of World War II.

The vertebrae, on the other hand,

are sent to leading anatomist John Barclay

from Edinburgh's most successful school of anatomy.

He concludes that this is unlike any other creature

he's ever seen, opening the door to the possibility

that this is a newfound species.

HEIDI: The connection isn't initially made

to the Loch Ness Monster, because it's not the 1930s yet,

so Nessie fever has not swept the nation.

The legendary creature is not famous yet.

But once it becomes famous, theorists realize,

"Hold on, this might be the same animal."

LAURENCE: The fact that Stronsay is just 120 miles from Loch Ness

earns extra attention.

And the physical description of the two creatures

is strikingly similar.

Gray skin, long neck,

some kind of flipper-like appendages, small head.

The only real major difference I would say is the size.

The Stronsay Beast according to those eyewitnesses

is much larger than anyone has ever claimed

the Loch Ness Monster to be-- nearly twice the size.

That doesn't necessarily rule out the same species though.

Perhaps Nessie is just smaller.

DUSTIN: Or, there's an even more compelling idea.

What if the creature in Loch Ness

is a younger specimen?

What if the loch is where these animals breed?

It certainly happens.

Salmon swim in all the way from the North Sea

and breed in the River Ness and the loch.

It's an annual event.

LAURENCE: This may also explain the inconsistency of sightings.

ZAK: If that's the case, the animal breeds

and raises its young in the loch,

but then it migrates out into the sea.

So, the reason people don't see it all that often

is because it doesn't live in Loch Ness full time.

KRISTYN: It's possible.

Loch Ness and Stronsay are actually connected by water.

Both the Caledonian Canal and the River Ness

connect the loch to Rosemarkie Bay,

and ultimately the North Sea.

So, it's entirely possible that whatever washed up

on the Isle of Stronsay is the same species

as the Loch Ness Monster.

LAURENCE: If the Loch Ness Monster exists,

the waters it lives in remain largely unexplored.

But as marine science evolves,

new theories emerge about what Nessie might be.

Over time, modern technology has allowed scientists

to dive deeper into bodies of water than ever before.

And the diversity of life there is amazing.

ZAK: And the more species we discover,

the more we have to compare to the Loch Ness Monster

to see if they're a match.

LAURENCE: And that approach has yielded

one particularly compelling candidate.

In 2012, biologist Jeremy Wade publicizes a theory

that some scientists have held for years

on the origins of the Loch Ness legend.

Nessie may in fact be a creature that scientists already know--

a highly-elusive, very mysterious species,

but one that is very real.

The Greenland shark.

DUSTIN: Why a Greenland shark?

Why this animal in particular?

Upon first blush, this theory seems way out there.

For decades Nessie has been described

as more of a dinosaur-like creature.

But that belief stems from a photo

that we now know to be a hoax.

LAURENCE: What if Nessie is not the long-necked beast

in the surgeon's photo, but something else entirely?

KRISTYN: Like Nessie, Greenland sharks are elusive.

They tend to prefer very deep, very cold water.

That makes them hard to study.

They are rarely photographed or filmed.

A lot of what we know about them has only come to light

in the past couple of decades,

despite the fact that our best guess

is they've roamed the Earth for over 100 million years.

DUSTIN: In fact, the first time one was photographed

wasn't until 1995.

And when you first look at it,

you may not initially see Nessie, but keep looking,

and think about some of the eyewitness accounts.

It could fit.

LAURENCE: Greenland sharks are typically mottled gray

or brown-- the same colors used

to describe the Loch Ness Monster.

And they're big.

Greenland sharks can get to like 20 feet long

and like four tons.

So, they're very, very large animals.

They can actually be larger than great whites.

LAURENCE: Unlike most sharks, they have a small dorsal fin.

ZAK: If a normal shark were cruising along the surface

of Loch Ness, people would know it,

it's instantly recognizable.

But the odd, stubby fin of the Greenland shark

could easily be mistaken for something else--

possibly the head or a hump of some kind of sea monster.

DUSTIN: Which definitely applies to most sightings of Nessie.

Witnesses often describe multiple humps

undulating through the water.

When you think back to the time of Saint Columba,

through the Middle Ages, and the Nessie sightings

even up to the 1800s, there are still people around

who believe in things like mermaids

and all kinds of fantastical creatures.

So, it's not surprising that somebody could catch a glimpse

of a bizarre-looking shark like this and think

that it is a monster in Loch Ness or the River Ness.

I mean, it kind of does look like a monster.

LAURENCE: According to some scientists,

Greenland sharks also move like the Loch Ness Monster.

So, most people imagine sharks as being fast agile hunters.

You think of like a great white or a mako shark

chasing down a meal.

Nessie sightings tend to describe a slow-moving animal.

JONATHAN: Greenland sharks live

in a completely different habitat

where the water's really cold,

and they have a very slow metabolism.

So, they swim slowly, they eat slowly.

They do everything slowly.

DUSTIN: That is why they're sometimes called sleeper sharks.

If an enormous Greenland shark surfaced

and moved along the water of Loch Ness that slowly,

it's easy to see how it could be misconstrued

as something other than a shark.

ZAK: And why don't we see Nessie very often?

Because a shark doesn't have to come up for air.

It may occasionally make its way to the shallows,

but not very often.

These Greenlands love the depths.

KRISTYN: The problem with the Greenland shark theory

is that Loch Ness is a body of fresh water.

For a long time we've thought that Greenland sharks

are saltwater creatures.

LAURENCE: But new evidence suggests otherwise.

Greenland sharks have recently been filmed

in Canada's St. Lawrence River.

KRISTYN: In fact, they go all up and down the St. Lawrence Seaway

through America and Canada, and that is entirely freshwater.

LAURENCE: A similar freshwater route

connects Loch Ness with the North Sea.

DUSTIN: If Greenland sharks can live in both freshwater

and seawater, it's entirely possible

one could survive in Loch Ness,

or at least migrate in from time to time.

ZAK: Maybe there's even a chance that the Stronsay Beast remains

were misinterpreted, and it was some kind of large shark

that was capable of going back and forth

between the sea and the loch.

All of this evidence excites the scientific community.

There are so many similarities between Greenland sharks

and Nessie, experts think that they've solved the mystery.

LAURENCE: A 2016 experiment at the University of Copenhagen

only adds to that excitement.

These scientists take 28 Greenland sharks,

and have them radiocarbon dated to determine their age.

Shockingly, one of them is over 400 years old.

ZAK: 400 years makes the Greenland shark

the world's longest living vertebrate.

To give you an idea of how incredibly old this is,

there could be a shark swimming out there that was alive

before the Pilgrims left England on the Mayflower.

The team also finds that these sharks

only grow about a centimeter every year,

and they don't even reach sexual maturity

until they are about 150 years old.

ZAK: For some, this seals the deal

that the Loch Ness Monster is a Greenland shark.

That longevity could be key

to how isolated the sightings have been.

Nessie seems to be a solitary creature.

No one has ever seen two at once.

Most animals, you would need a family of them

living in the loch and regularly breeding

to account for so many years of regular sightings.

One single Greenland shark could be responsible

for all of the sightings dating back to the 1600s.

LAURENCE: To find out if a Greenland shark

is living in Loch Ness,

a team looks for proof in 2017.

A team of scientists led by Dr. Neil Gemmell

from the University of Otago in New Zealand

did a really interesting study.

They went to Loch Ness and they took water samples

all over the lake-- the middle,

the sides, the ends, everywhere.

From a half a liter of water,

we can get a very, very good catalogue

of life within the loch.

JONATHAN: They did a DNA analysis of all the DNA

that they found in that water.

So, in theory, any living creature

that has been in that water would leave a DNA trace.

ZAK: If there's a shark in there, they'll know,

along with anything else that might be swimming around.

LAURENCE: After two years, on September 5th, 2019,

they announce their results.

First and foremost, they found no evidence

of Jurassic-era animals, including plesiosaurs.

ZAK: But more importantly, they found no evidence

of shark DNA, including Greenland sharks.

KRISTYN: If we think the creature might be migrating

in and out of the loch,

and maybe it's been away for a while,

perhaps the shark is still a candidate for Nessie.

But that DNA test makes things a whole lot less likely.

ZAK: This study wasn't completely fruitless though,

because they did find the DNA of countless other species,

including an incredibly large deposit

of another potential Nessie candidate.

Across nearly 1,500 years of sightings,

witnesses and scientists alike have been fascinated

with the mystery of Scotland's beloved Nessie.

But a closer look at results from a 2019 DNA test

might finally reveal the secrets of what's living in Loch Ness.

ZAK: Throughout the years, since at least the 1960s,

and maybe even before, modern technology has been used

to try and solve the mystery of the Loch Ness Monster--

everything from sonar, to thermal imaging,

to hydrophonic soundwaves.

But none of these techniques have given us concrete results

or gotten us any closer to legitimate answers.

However, anybody who has ever watched a crime show

knows that the best evidence to provide the identity

of the culprit is DNA evidence.

LAURENCE: In 2019, a team of scientists from New Zealand

finally complete their DNA analysis of water

from Loch Ness.

While there's no trace of Greenland sharks,

what they discover unleashes new possibilities for Nessie.

They find about 3,000 species, if you can believe it.

Most of those are tiny plankton, roundworms,

nematodes, small crustaceans.

Of the larger fish, they find salmon, pike,

stickleback, lamprey, a few others.

They even find DNA of land-based creatures

that sometimes end up in the water

for one reason or another, including dogs, cattle,

sheep, rabbits, and even humans.

This tells us that this test is very sensitive.

Even animals that rarely go in the loch are detected.

But the largest amount of DNA they find

that is detected in almost every single sample

is eel DNA.

JONATHAN: There are a ton of eels in Loch Ness.

It is one of the principle spawning grounds

of the European eel.

Now, most of these eels, they only grow

to be about 0.8 meters.

So, they're not exactly monsters,

But could there be a monster eel?

Very possible.

Every single sampling site that we went to pretty much had eels.

And the sheer volume of it was a bit of a surprise.

KRISTYN: The largest eel in the region

is the European conger.

It can grow to almost 10 feet long

and weigh up to 160 pounds.

Could that be Nessie?

JONATHAN: Eels are migratory fish,

so if someone saw an eel in Loch Ness,

it's pretty easy to assume that they could think

that that's the Loch Ness Monster.

ZAK: Once you have an eel in mind, and you look back

at the videos and images of Nessie,

you realize it could be possible.

LAURENCE: Especially if you analyze the way

both Nessie and eels move.

The Loch Ness Monster has often been described

as a serpentine-like monster,

maybe snake-like, or perhaps, eel-like.

If any animal could look like a sea monster,

an eel is a prime candidate.

It really has a classic serpentine look.

Eels move in a slithery, sort of snake-like way,

where their body curves, and that's exactly what people

say the Loch Ness Monster looks like.

So, it's really possible that they saw an eel

with those hump-like shapes, and they thought,

"That's the Loch Ness Monster."

LAURENCE: A 2007 video shot by retired engineer Gordon Holmes

seems to support this theory.

DUSTIN: In 2007, Holmes makes some trips to Loch Ness

to perform some amateur experiments,

just for fun.

KRISTYN: At first, he records some sounds

using hydrophonic equipment.

Then he sets up a camera to capture video of the lake,

but he doesn't find anything out of the ordinary.

LAURENCE: That is, until his visit on May 26th.

DUSTIN: Holmes spots some movement in the water

as he's driving, and pulls over and grabs his camcorder.

His footage clearly shows some type of large animal

moving through the water.

Though it's hard to tell, it appears as though it's moving

in a serpentine fashion,

almost slithering through the loch.

KAREN: This is some of the best video ever captured

of a creature on the surface of Loch Ness.

Holmes purposely zooms in and out while he's shooting

to make sure the shoreline and other landmarks are visible,

so the footage can be analyzed later.

LAURENCE: Holmes sends his footage to a forensic team

to determine the animal's size and speed.

They find that it's 10 to 15 feet long

and swimming at a speed of six miles per hour.

Based on movement analysis, they find a strong likelihood

that this animal is an eel.

Eels are the most common animals in the loch,

and it's very likely that most of the sightings over the year

have been related to eels.

ZAK: At the time, this is long before the discovery

of eel DNA in the loch,

so they come to this conclusion all on their own.

KRISTYN: Eels can also appear brownish gray in the water

and have very smooth skin like the Nessie descriptions.

The so-called "humps" that people see

could be the serpentine curves of the eel as it swims.

And the whole "long, thin neck" concept

could fit with the eel as well.

They have a long, thin everything.

DUSTIN: But at 10 to 15 feet long,

if Holmes' research is correct,

that would still be an eel of massive proportions.

And in fact, they did develop an amazing new science

and a way to study bodies of water

and what lives in them.

ZAK: But of course, potentially identifying

the Loch Ness Monster brings a ton more attention

to their research.

LAURENCE: When a DNA profile of life in Loch Ness

is completed in 2019,

it uncovers a wide array of species,

but it doesn't identify everything.

Some of Nessie's most passionate researchers

are quick to note that according to the full 2019 report,

the source of 20% of the DNA collected is unknown.

And that opens up a whole new world of possibilities.

Maybe the monster isn't a plesiosaur, or a shark,

or an eel, or any species

that we've even encountered before.

All of the previous attempts to prove that it is this animal

or this other animal have been destined to fail

because it's none of these.

KAREN: We may not know what it is

because we just don't know what it is.

Based on all this unidentified DNA,

could Nessie be a completely undiscovered,

previously unknown species?

JONATHAN: If there's one thing that all underwater explorers

and scientists can agree on, it's that we have not found

all the species in the ocean.

There are hundreds of thousands, maybe millions of species

that we haven't found or classified yet.

There's stuff out there that we don't know anything about.

LAURENCE: If Nessie's species is unknown,

how can we ever identify it?

Pretty much the only way we can properly identify

a new species-- whether it's a tiny insect

or a giant lake monster-- is to find a specimen.

That's how science proves and classifies new animals,

plants, and even bacteria.

Either living or dead, we have to capture one.

KRISTYN: As far as we can tell, nobody has ever captured

a Loch Ness Monster.

There may have once been those remains

on the Isle of Stronsay,

but we're not actually sure it's the same animal.

And in any case, none of that DNA survived.

So, there's no way to compare the Stronsay Beast DNA

with the unknown DNA that we have from the Loch.

DUSTIN: So, we're stuck with trying to catch

this elusive animal in Loch Ness.

But for 1,500 years no one has even come close.

We're still trying to get a good photograph,

let alone trap the thing.

LAURENCE: The problem lies

in the incredibly challenging conditions at Loch Ness.

JONATHAN: First off, Loch Ness is huge.

It's 23 miles long, it's a mile wide,

and the most important thing, 750 feet deep,

which is impressively deep for any lake.

It contains more water than any other lake in the UK.

In fact, it contains as much water

as all the lakes in England and Wales combined.

So, it's a large place to look for a monster.

KAREN: But the size isn't the only reason

it's hard to explore.

Loch Ness is full of peat,

which is organic matter from plants

that's constantly breaking down in water.

It makes the water dark brown, almost black.

Visibility is only a couple of feet at most.

And even if you were to dive down for a look around,

the temperature is not survivable.

Loch Ness has an average surface temperature

of 42 degrees Fahrenheit.

And as soon as you get about 20 feet down,

it has what is known as a thermocline.

It's a stratification of the water,

almost like an invisible wall, where suddenly the temperature

can drop 10 or 20 degrees.

Without a very advanced modern dry suit,

a diver could freeze to death and drown in about six minutes.

KRISTYN: I'm not sure that this thing

is possible to catch in Loch Ness.

LAURENCE: But could another lake linked to Loch Ness

by a waterway offer fresh hope

of capturing a creature like Nessie?

According to some, the answer is yes,

and Sweden's Storsjön Lake is the ideal location.

DUSTIN: Both are freshwater and fairly cold.

Both share similar biological diversity,

oxygen levels, et cetera.

If something can live in Loch Ness,

it can most likely live here too.

LAURENCE: Like Loch Ness, it has a long history

of monster sightings.

There have been centuries of reported sightings

of a creature with the same physical description.

In Swedish, it's called Storsjöodjuret,

which literally translates to "The Great Lake Monster."

It's first written about on a runestone

that dates all the way back to the year 1050.

It's got this depiction

of a long serpentine water monster on it.

LAURENCE: Conditions in the two lakes are similar,

but there's one key difference.

Storsjön Lake is much cleaner and clearer,

and much less hazardous to explore.

LAURENCE: And that makes spotting a monster much easier.

ZAK: Thanks to much more favorable conditions,

the Storsjöodjuret has been captured

easily on video from far away,

most recently in a 2008 documentary

that also shot infrared footage.

And attempts to track the specimen

have already been mounted.

LAURENCE: Researchers at the Lake Monster Center in Storsjön

plan to continue their search efforts.

If they're successful, all we have to do

is compare the Swedish creature's DNA

to all the unknown DNA from Loch Ness.

If any of it matches, we've identified our monster

and discovered a brand-new species.

That would be among one of the most incredible

scientific discoveries in history.

KAREN: As many as 18,000 new species

are identified every single year.

So, the possibility is out there.

I hope one day we can add Nessie to that list.

LAURENCE: Over long centuries, many theories have emerged

about the origins and existence

of the mysterious Loch Ness Monster.

Each offers an intriguing possibility,

but none are airtight.

You say, hey, maybe it's a plesiosaur,

but there's no evidence any of them survived extinction,

and we'd see an air-breathing creature much more often.

KAREN: So, maybe it's a Greenland shark,

but shark DNA wasn't found in the loch.

ZAK: Well, what about all the eel DNA?

But could an eel, even a giant one, grow that big?

What about the thing that washed up in Stronsay?

Or the similar lake monster in Sweden?

HEIDI: To be honest, any one of these creatures

could be what was spotted in Loch Ness,

or perhaps it's more accurate to say

all of these things could be.

LAURENCE: What if it's not Loch Ness Monster,

but monsters?

DUSTIN: We talk about the Loch Ness Monster

as this monotypic creature, like there's just one of it.

There's only ever been one Nessie.

But given the time period, 1,500 years of sightings,

that's highly unlikely.

There's absolutely no reason it has to be one thing--

and the same thing-- over centuries.

KRISTYN: Let's start with the eel theory.

For sure, some of the things that people have seen

in the loch over the years have been eels.

Just look at the Gordon Holmes footage,

and that's obvious.

KAREN: It's a common animal in the loch,

and when you're scanning from far away

looking for any kind of movement on the surface,

a large swimming eel could certainly catch your attention.

ZAK: How about a Greenland shark?

Well, we know they're swimming around in the North Sea,

and they can and do sometimes go up river

in the freshwater areas.

It's quite likely a predator like that

could follow a bunch of salmon into the River Ness

and could conceivably make it all the way into the loch.

A lot of animals that sharks like to eat

make that trip, including seals.

While there wasn't any shark DNA in 2019,

there is still a good chance that a shark has been spotted

in the loch across the thousands of other sightings.

LAURENCE: And what about the plesiosaur theory?

HEIDI: I don't necessarily think

there's a living, breathing plesiosaur

that is swimming around there.

But I do think the plesiosaur may be what's behind the legend.

Scotland and the UK in general

are teeming with plesiosaur fossils--

fully-intact skeletons of creatures

that back in the Middle Ages would have been assumed

to be monsters.

Water beasts, just like Saint Columba saw.

Imagine in 500 or 600 AD,

you stumble upon the remains of a plesiosaur.

You would certainly tell your buddies back at the ale house

about the crazy giant long-necked creature.

It's quite possible that this tale eventually morphed

into the Loch Ness Monster legend.

HEIDI: As for the Stronsay Beast,

whatever it is, it really doesn't matter.

If it washed up on the shore of the island,

we know there's a direct path of waterway

that connects back to the Loch Ness.

KRISTYN: And any migratory creature,

whether it's a shark, a whale, or anything less,

could be swimming back and forth from the sea to the loch.

HEIDI: Some of the Loch Ness sightings

could be the same animal.

LAURENCE: Or perhaps an unidentified animal

from even further away.

KAREN: Across 1,500 years, some of the Loch Ness sightings

may well be an unidentified new species.

Even the DNA results bear that out.

They can't identify every living thing in the loch.

KRISTYN: But if Sweden's Storsjön Lake

is hiding the same species,

maybe we'll have an incredible discovery soon.

DUSTIN: Still, even if they identify the Storsjöodjuret

and identify one in Loch Ness as well,

that doesn't mean that Gordon Holmes didn't see an eel,

or others didn't see other animals.

A new species would be a revelation,

but remain only one piece of the puzzle.

HEIDI: And still, there will always be those people

who believe Nessie is a hoax.

We know for a fact that plenty of Nessie witnesses

have been duped by hoaxes.

It happened to a sonar team that found a movie prop.

And in fact, it happened to millions of people

around the globe, thanks to the surgeon's photograph.

DUSTIN: So, yes, Nessie is also a hoax,

but not just a hoax.

There's much more to the monster than that.

KAREN: One day, we may get the perfect biopsy,

the perfect picture, the perfect bone specimen,

or maybe a strange long-necked creature

will just walk right out of the loch and say hello.

And when that day comes, it'll be time

to break out the champagne.

ZAK: But until then, I think we shouldn't limit our minds

to what Nessie could or couldn't be.

Because it could be something new next year.

DUSTIN: The possibilities are endless,

and that is what has kept people

fascinated with Nessie for so long.

Despite the many challenges,

thousands of amateur and professional researchers

still spend time at Loch Ness every year

hoping to unmask the monster.

Perhaps modern technology will soon provide us

with a clear picture of what's hiding in the depths.

Until then, there's no shortage of people willing to look.

I'm Laurence Fishburne.

Thank you for watching "History's Greatest Mysteries."