Original subtitles

A German U-boat sunk by a colossal sea serpent...

...a remote fishing village terrorized by a giant

man-eating lake monster,

and horrific unidentified sea creatures

that defy explanation.

For centuries, tales have been told

of frightening encounters with strange creatures

living deep beneath the water's surface.

The stories include sightings of giant sharks,

prehistoric serpents, and even

razor-toothed mermaids.

Might these terrifying creatures

be the real-life versions of legends and myths?

Perhaps.

Because, every year, biologists discover

thousands of new and frankly bizarre species

in Earth's vast aquatic realm.

Could our planet's blue expanse be hiding

actual monsters within its watery depths?

Well, that is what we'll try and find out.

♪ ♪

SHATNER: The Atlantic Ocean. 2022.

Off the coast of Rhode Island,

researchers from the Atlantic Shark Institute

sweep the ocean depths with sonar--

a technology that uses sound waves

to create underwater images.

To their dismay, they discover something massive

swimming underneath their boat.

Suddenly, on the sonar screen, was the shape of a giant shark.

You could see the fin, the face.

It was about 50, 60 feet long. And for a moment there,

everybody on that ship just froze.

There's a shark of unimaginable proportions

just under this boat.

PHILLIP STERNES: There was a 50-foot sonar ping

that resembled a very large shark,

which is quite extraordinary.

Many people online started to speculate that

it was our first evidence

that there is a large shark out there, possibly megalodon.

Megalodon was an extinct huge shark that existed

from about 23 million years ago

to about three and a half million years ago.

Recent estimates puts the shark up to about

80 feet in total length.

So, it's two yellow school buses lined up front to back.

So, the sonar image was pretty exciting.

However, the researchers, including myself,

hypothesize that this was probably just

a huge school of fish that just happened to be swimming

in a shape that resembled a shark.

OCKER: The image of the creature or maybe school of fish

on the monitor immediately went viral.

Everybody was sharing this.

And what this tells us is we are so fascinated

with giant sharks and megalodon itself that

even a momentary blip on a screen

is enough to send everybody into excitement and conjecture.

SHATNER: While conventional wisdom tells us that the megalodon

went extinct over three million years ago,

this story reinvigorated a truly terrifying question:

Is it possible that the mighty megalodon

is still out there in the vast ocean?

The reality is this terror of the deep

remains a fascinating mystery

pieced together one tooth at a time.

Megalodon was the most ferocious, incredible shark

that ever lived.

Scientists estimate that it weighed

about 50 to 75 tons.

Its bite pressure was about 40,000 pounds per square inch.

Its bite force was tremendous.

Recent studies have shown that not only could've the megalodon

been the biggest apex predator of its time, but ever.

We know that because we've found the teeth.

The megalodon tooth is around seven inches,

which means it would be a 65-foot apex predator.

And so, we know the size,

but to really understand what the shark looks like,

it's still a mystery.

We haven't found a fossil of a megalodon

because sharks are mostly cartilage.

That breaks down.

Megalodon is in the same order that the great white is,

so it's easy to assume that the megalodon

looked like a big version of a great white shark,

but that's not necessarily true.

Science is always building on itself,

and-and this is one more example.

SHATNER: If megalodons existed millions of years ago,

why would we even consider the possibility

that this colossal predator might still be around today?

Or could there be a relative of this prehistoric terror

that has yet to be identified?

Perhaps clues can be found in a 1900s tale

of frightened fishermen off the coast of Australia.

In 1918, in Port Stephens in Australia,

fishermen were terrified and refused to go back

out onto the water

because they had seen something out there that had scared them.

They told of being fishing for lobster in deep waters.

For several days, they noticed something

was attacking their pots and stealing their catch.

And then, one day, the crew noticed

a ghostly white shark pass by them.

They estimated it to be between

100 feet and 300 feet in length.

Far larger than any known living shark.

LYLE BLACKBURN: This was documented

by naturalist David Stead,

who said that the men were insistent

that this was not a whale.

They recognized this as something

they had never seen before.

So, the question is, what did they really see?

SHATNER: While some experts proposed that the fishermen saw

a whale shark-- the largest known fish on Earth--

they don't reach anywhere near the size

of the shark said to have been spotted in 1918.

And this is not the only story

of the mysterious predators off the coast of Australia.

In 2003, a great white shark was reportedly swallowed

by a massive, unknown creature.

And in 2019, an Australian fisherman

was reeling in a large mako shark

when something terrifying bit the mako in half.

DAVE RIGGS: There are photographs around

of animals with really big bites in them.

And those bites allude to other large apex predators

being of colossal proportions.

I think there could be something out here

that we're not aware of, that we don't know about.

We actually know nothing about the ocean.

And my hope is that

the pursuit of the unknown

is enough of a driver

for people to stop and appreciate

and respect the unknown.

SHATNER: While Australia is certainly known

for its giant, deadly sharks,

stories of unidentified ocean predators

can also be found all over the world.

In 2024, it was widely reported

that another large shark was swallowed

by an unidentified carnivore off the coast of Bermuda.

So, in 2020, a group of researchers

tagged a porbeagle shark.

Now, a porbeagle shark is a pretty large fish.

Between eight and 12 feet long, an apex predator.

And then, over the course of the next months,

it started going to much deeper levels of the ocean

where porbeagle sharks usually aren't.

And the researchers had to conclude

that tracking mechanism they put on the porbeagle

is now in the belly of some other creature.

So now the question is,

what could eat an apex predator? They don't know.

SHATNER: Could a creature like the mighty megalodon

be stalking the seas beneath us?

Well, it's a frightening thought

and a fascinating mystery

that has both terrified and tantalized us for centuries.

There's a real sense of vulnerability

when you are out on the water.

The fathomless nature of the ocean

when you can't see the bottom.

There's a, just an incredible sense of

one's own smallness in the universe.

And that's where we start getting into that realm

of folklore and mythology and the fantastic.

The belief in sea monsters is unbelievably pervasive.

We do know that this world was populated

by massive, ancient creatures

long before we were on the scene,

and the presence of their fossils might suggest that

some of those creatures survived in a way

that made it into the oral traditions

of contemporary cultures.

If we have water, we will put monsters in it.

SHATNER: The Flannan Isles, Scotland.

December 26, 1900.

A ship named the Hesperus arrives

at the tiny, rocky outcrop of Eilean Mòr,

about 80 miles west of the Scottish mainland.

The ship is there to bring provisions to the three lone men

living on the island-- James Ducat,

Thomas Marshall, and Donald McArthur--

who are stationed there as keepers

of the Flannan Isles Lighthouse.

OCKER: In 1899, they erected a lighthouse

on Eilean Mòr, which is one of the Flannan Islands,

to make sure people didn't ground ashore on this island.

Eilean Mòr is small, 40 acres.

It's basically a rock with some grass on it

in the middle of the ocean.

The coast is cliffs,

so there's ramps and stairs and railways.

Usually, there's a crew of lighthouse keepers there,

three people, they live on the island.

They're always there to maintain this light.

In 1900, ships started noticing the light was out.

When the supply ship finally arrived to bring supplies

and to recrew the lighthouse...

...they found nobody there.

LEWIS: It was as though they stumbled onto a crime scene.

The clock on the wall had stopped.

The table had been set for a meal,

but it hadn't been served.

A chair was knocked over.

It looked as though the men had raced out of the house

for some reason.

But they could not put the puzzle pieces together

as to what happened to these missing lightkeepers.

McCLOSKEY: The master of the Hesperus decides to have

the whole island searched.

What all of them find deeply unsettling

is the damage that's happened to the west landing.

Concrete has been torn apart.

The railings have been pulled out.

The turf at the very top of the island--

which is up to 180 feet above sea level--

has been chewed up, the rocks have been thrown about.

It's inexplicable what's happened.

They've never seen anything like it before.

Despite extensive searches

and people investigating over the decades,

there was no trace of them ever found.

SHATNER: What could've possibly happened

to the three men stationed

at the Flannan Isles Lighthouse over a century ago?

The lack of obvious clues

has led some to unsettling speculation.

There's several theories about

what happened to the three keepers.

There's murder,

that they were swept away by a giant wave...

...but one of the theories is the disappearance

was caused by a sea monster.

Scotland is surrounded by water.

And it is known as an area

where sea monsters were believed to roam.

SHATNER: Scottish folklore includes many monsters

associated with the dark waters off its rugged coast.

But perhaps the most terrifying of them all

is a truly massive sea serpent known as the Cirein-cròin.

BLACKBURN: The name Cirein-cròin translates to "gray crest,"

which was due to a large, fan-shaped fin

that ran down the length of its body.

It was said to also have the powers to shapeshift.

It could transform itself into a smaller fish,

which could then be caught by fishermen

and pulled onto the boat.

At that point, it could shift back into its regular form

and destroy the ship, devour the sailors.

This was a frightening sort of creature.

McNEILL: The Cirein-cròin is gargantuan.

According to folklore, this is a creature that would make

a meal out of seven whales.

And it lives off the coast of Scotland,

where there's all of these outlying islands

where people are making their living,

working in the sea as fishermen.

So, this is a relevant story to their lives.

Many have proposed that the Cirein-cròin

was responsible for the missing lighthouse keepers.

When you take into account of all the damage that was there,

it would've taken something with immense power.

That's exactly where they believed

the Cirein-cròin came in.

SHATNER: Could a legendary monster really have been responsible

for this mysterious disappearance

at the Flannan Isles Lighthouse?

Surprisingly, some believe there's actual evidence

that a dangerous sea serpent lurks in these dark waters.

In 1808, a massive unidentified carcass

washed ashore at one of Scotland's Orkney Islands.

It became known as the Stronsay Beast.

The Stronsay Beast attracted a great deal of interest.

It had a long, serpent-like body

and the whole thing is very, very long.

And there was no known answer for what it actually was.

So, these animals, these creatures were huge.

It's quite possible that they also sunk ships.

BLACKBURN: In 1918, during World War I,

a German U-boat, UB-85,

was navigating the waters between Ireland and Scotland

when they were sunk.

And the captain of the ship, Günther Krech,

claimed that the reason the boat sunk

was because of some huge creature

that rose out of the water

with horns and glinting teeth,

and it damaged the boat.

LEWIS: Eventually, the creature went back

into the depths of the water.

Unfortunately, the damage had been done.

The U-boat is starting to sink.

Just before it makes its way to the bottom of the sea,

the British arrive and are able to save the crew.

That's when the German captain begins his story

of the horrific sea monster.

SHATNER: Could the multiple reports of so-called sea monsters

offer some proof that the local Scottish folklore is true?

And could a real terror of the deep be responsible

for the disappearance of three unfortunate lightkeepers

over a century ago?

The Flannan's mystery is basically a story

of three lighthouse keepers who disappeared

into thin air in 1900.

The biggest question for me is what happened

to the bodies of the men?

It could be said that, if they had fallen into the water,

wherever they are, most times,

one of them will wash up somewhere.

But the bodies just completely disappeared.

If they had been taken by a giant sea monster,

they would've been eaten.

I've never discounted the-the sea monster theory

because people still don't know what lies under the ocean.

Are the waters off the coast of Scotland inhabited

by a dangerous sea serpent?

Without any physical proof of the monster,

all we can do is speculate.

But in Japan, the discovery

of a bizarre mummified creature

may provide the truth behind the legend

of a hideous,

razor-toothed mermaid.

SHATNER: This small coastal town is home to

the serene Buddhist sanctuary known as the Enju-in Temple.

Here, a very peculiar artifact

is carefully enshrined in a fireproof box.

It is the resting place of a grotesque,

mummified creature known as a ningyo.

There's probably stories that date back

to the eighth century in Japan about ningyo.

So, ningyo is usually translated into English as "mermaid."

When you first look at it, it is quite horrifying.

And it does look to be like some kind of half-human, half-fish.

It's about a foot long.

And it has two hands, which it's holding up to its mouth,

and its face looks to be screaming.

It's just totally, just a mystery.

SHATNER: While it's unclear how or when this ningyo mummy

came to the temple,

the only tangible clue

is a handwritten note that says the creature was caught

in a Japanese fishing net

sometime between 1736 and 1741.

And despite its murky history,

today, the Enju-in Temple's 34th chief priest,

Kozen Kuida, is its dedicated caretaker.

(speaking Japanese)

(translated): There are many legends about mermaids in this area.

There is an old legend that, if you eat the blood

and flesh of a mermaid, you will live a long life and never die.

Visitors to the temple in the past would peel off

and eat the scales, thinking it would grant them

a longer life or even immortality.

However, since this was harmful to the mummy,

we have asked visitors to refrain from doing so.

SHATNER: There are allegedly more than 14 similar ningyo mummies in Japan,

but tales of mermaids can be found around the globe

and have been told for thousands of years.

In ancient Syria, it is said that,

when the goddess Atagatis jumped into a lake,

she sprouted a fish tail.

In Thailand, folklore describes an ancient mermaid

named Suvannamaccha.

And the Melusine is from European folklore.

Many of these mermaids of myth and legend

can be quite deadly.

Mermaids, traditionally, are a half-woman, half-fish creature.

And this is something that, in literature

and in popular culture,

is often portrayed as sort of a peaceful,

beautiful creature that men and sailors

fall in love with easily.

And when we look at folkloric tradition,

they're actually pretty bloodthirsty and dangerous.

A beautiful woman with a fish tail

is often hiding multiple rows

of incredibly sharp razorlike teeth,

and you will be torn limb from limb by this very same creature.

SHATNER: Japan's mummified mermaid

certainly doesn't look like an object of desire.

The question is, just what is this strange, snarling specimen?

Well, in 2022,

that's exactly what Japanese researchers

were determined to find out.

The ningyo was sent to the Kurashiki University

of Science and the Arts for some experiments.

Led by Professor Kato Takafumi,

researchers performed CT scans,

X-rays, and DNA analysis on the artifact.

The results suggested that the specimen

was not a single creature,

but instead was pieced together artificially.

It was probably made in the late 1800s.

The teeth and the body is a fish,

and it has two hands made from different animal parts,

and there's lots of puffer fish scales all over it,

and some cloth and cotton thrown in

as well to bring it all together.

Once the researchers realized that this was artificially made,

the question immediately arises-- why?

Why was it made? Is it based on some kind of truth,

some kind of creature they saw out in the water?

That's the really big question when it comes to these ningyo.

They are all over Japan,

they're in temples, they are venerated, they are worshipped.

Why? Why do they exist? What inspired them?

The results have not changed my feelings or beliefs

that such a creature might have existed in the sea,

perhaps a half-human, half-fish being.

As I have always said, Buddhist temples

and statues of Buddha are merely objects made of wood or stone,

yet people still worship them with reverence.

There are many creatures that people believe exist.

Many things in the world remain undiscovered.

BLACKBURN: The specimen found in the Enju-in Temple is just

one of many of these alleged ningyo specimens

just waiting to be analyzed.

Could one of these specimens turn out to be proof

that mermaids do exist?

We just can't say for sure.

It's remarkable to think that modern science

may eventually prove that the fabled and frightening

ningyo actually existed.

But there's another terror of the deep

rumored to inhabit a lake in the northeastern United States.

A species believed to be so ancient

that it dates back to the time of the dinosaurs.

SHATNER: The South Pacific. April 1977.

30 miles off the coast of New Zealand,

a Japanese fishing vessel drags a massive net nearly 1,000 feet

under the water hoping to fill it with tons of mackerel.

The crew is shocked when the net pulls up a horrifying carcass

of a creature that will spark awe

and curiosity around the world.

This fishing boat picked up this enormous,

disgusting creature, and there is a famous photo

that you can see of it where it's hanging

from the boat's crane,

and the skin is kind of dripping off the bones.

It's got this long neck and these gangly arms.

Back in Japan, there was

a marine expert named Tokio Shikama.

And he was looking at the photos.

And he proposed that it might be a plesiosaurus,

which has been extinct for 66 million years.

LEWIS: The plesiosaur had razor-sharp teeth in its mouth.

It could get up to 40 feet in length.

Researchers believe that it would attack its prey

from underneath, from below, like the great white shark.

It had an extremely powerful bite force.

It was a deadly predator.

SHATNER: Did Japanese fisherman discover the decayed carcass

of a prehistoric predator?

It's an audacious claim.

Yet, throughout the 20th century,

there have been intriguing reports to suggest

that large, plesiosaur-like creatures are very much alive.

And of course, the most iconic example is said to reside

in a large lake in the Scottish Highlands

called the Loch Ness Monster.

The Loch Ness Monster is undoubtedly the most famous

alleged plesiosaur-like creature,

but it's not the only one.

There are many lakes and lochs around the world that have

stories of unknown creatures swimming in them.

One of the best examples is Lake Champlain

located between Vermont, New York,

and the province of Quebec in Canada.

Lake Champlain is 120 miles in length

and 13 miles at its widest point.

It's three times the size of Loch Ness.

And many people believe that a large lake monster

lives in the waters of Lake Champlain.

The Lake Champlain Monster, also known as Champ,

is described as having a large body,

and four fins, a long neck, with a small head,

very much like a plesiosaur.

SHATNER: The Lake Champlain Monster,

affectionately called "Champ" or "Champy,"

is a local legend for those who live

along this huge North American lake.

The creature is celebrated with historic markers that claim

hundreds of sightings of the beast,

and it's featured in museums as a large Jurassic plesiosaur.

But is Champ just folklore

or could there really be a monstrous creature

lurking the depths of Lake Champlain?

Lake Champlain gained international attention

in 1977 when Sandra Mansi

and her two children and her fiancé

were taking a leisurely drive up the coast

of Vermont along the lake.

They decided to pull over to have a little picnic,

let everyone stretch their legs,

and the kids to splash around in the water.

Sandra Mansi saw a large head

break out from the surface of the water

attached to a long neck.

Mansi was able to snap one photograph of the creature

that appeared to be looking away from her.

The photo shows what looks like

a plesiosaur-like creature with its body in the water

and its head and neck sticking up.

And this is something that's become

sort of the image of what we believe Champ to look like.

The Mansi photo has been analyzed by photo experts

who agree that this is a genuine photo

and has not been altered in any way.

It's very convincing that at least some sort of

mysterious creature is lurking in the waters of Lake Champlain.

SHATNER: Sandra Mansi's extraordinary photograph has provided

tantalizing proof of Champ's existence for half a century.

And what's even more remarkable is that it corroborates

sightings of the creature that people have described

in Lake Champlain for hundreds of years.

Champ is probably America's best known, um, lake monster,

and he's been around for a long, long time.

We see this reflected in the local Native lore.

The Abenaki had a name for this creature, the Gitaskog,

that was this monster inhabiting the lake.

Now, in their version, this is a serpentine thing with horns,

and some people have even suggested that this

could go much further back,

related to some other mythological creatures

and Native traditions.

SHATNER: Legends of a monster inhabiting Lake Champlain were already

well-established when Samuel de Champlain

discovered this body of water in 1609.

It is said that Champlain himself

spotted a large, unidentified creature in the lake.

And ever since, hundreds of eyewitness reports of Champ

have continued to accumulate.

Perhaps the most compelling recent evidence surfaced

in 2024, when filmmakers Kelly Tabor

and Richard Rossi were reviewing aerial footage

they shot over Lake Champlain

and noticed that they captured something extraordinary.

We were just getting an aerial shot of the lake.

The water is clear. It's-- it was a nice summer day.

We're out on our rickety 12-foot long rowboat

in the middle of Lake Champlain,

not even realizing there's this huge creature

that we caught swimming right behind us.

Champ is following our boat from behind,

swimming under the surface of the water.

When I saw the video of Champ swimming behind

our boat after the fact, it gave me chills.

I just started to shake and get tremors.

And I felt this fear, this awe

of just how massive and how close it was, just yards away.

We weren't looking for Champ.

We weren't expecting anything like this.

I've contacted scientists with earned doctorates, and

those in this field say that it has the body of a plesiosaur,

and it's moving, it's swimming, and it's bigger than your boat.

And so, this is a real game changer

if this creature has survived.

Could there be a living, breathing relic

from the age of dinosaurs

lurking deep in the waters of Lake Champlain?

It's an intriguing thought.

But there is a lake in Alaska

that holds an even bigger mystery

because locals have long believed its frigid waters

are home to a creature so big and so powerful

that it can sink boats with a single bite.

SHATNER: 200 miles southwest of Anchorage

lies the largest body of fresh water in the state,

Lake Illiamna.

At over a thousand square miles,

this massive lake is roughly the size of Rhode Island.

And from its southern shore,

onlookers notice a strange disturbance in the water.

NATHAN HILL: It was a relatively calm day and sunny, good visibility.

I happened to have my phone with me, and

we witnessed something emerge out of the water, and, uh,

I caught it on video.

What you could see was a shape,

and the shape was smooth and rounded.

It was very dark in color.

And it-it kind of came out of the water and

submerged itself back under the water.

I had my binoculars, and I was glassing out to the islands,

and these humps appeared, and these things were huge.

NIELSEN: I doubt if there's anything out on the lake

that can match that size.

It made your heart race a little bit

because these were, like, I can't stress it enough, big.

SHATNER: What was this huge creature breeching

the surface of Lake Iliamna?

To this day, no one knows for sure.

Yet, for centuries, Native inhabitants of this area

have claimed that it's an unidentified terror

known as the Lake Iliamna Monster.

There's many, many supernatural aquatic creatures

in the Native lore and contemporary legends of Alaska.

These things are known in the stories for eating people,

for capsizing boats, for causing death and destruction.

Maybe none are more famous or more well-known

than the Lake Iliamna Monster.

The locals even had a name for this,

something like "the large black fish."

LEWIS: Since the 1940s, there have been credible sightings

of something big, ten to 25 feet long,

that has a broad, anvil-like head

that it uses to smash into boats.

And Lake Iliamna is very difficult to get to.

It's very secluded.

If there's a perfect habitat for a lake monster

to reside in, it's Lake Iliamna.

SHATNER: What is this dangerous large black fish

said to lurk the depths of Lake Iliamna?

After decades of speculation, in 2015,

retired pilot Mark Stigar

and marine ecologist Bruce Wright

decided to identify the monster once and for all.

BRUCE WRIGHT: Mark and I talked to local people,

and they were telling all these different stories.

I had some people draw some pictures of it.

Surprisingly, some of the pictures looked

a little bit like sleeper sharks.

And they can get up to 20, 21 feet,

22 feet, something like that.

They're pretty big fish.

And they're in Alaska all over the place.

I told Mark, I said, you know, we could solve this

maybe right away by trying to catch it.

MARK STIGAR: We started putting these large hooks baited

with a full salmon head down

on the bottom of the, uh, lake

and left them out there overnight.

There were 14 hooks designed to catch halibut

for commercial halibut fishing.

And we baited it with 14 fish heads.

We put it in over 100 feet of water with the intention

to come out every day,

check the line, so if we did get the animal on the line,

we could take a picture to figure out exactly what it is.

SHATNER: Mark and Bruce spent two years

setting and checking their bait without much luck.

But one day, when they pulled up their equipment

out of the water, they were shocked at what they found.

Something's taken our bait.

The 38-pound anchor had been, uh, moved at least 50 yards.

STIGAR: We pulled up, basically, a knot

of the entire rope, minus the anchor.

STIGAR: And all the hooks and everything were all tangled up.

The parts that the hooks

were attached to were totally ripped off the line.

For me, at that point in time, it was,

okay, there are no doubts.

There is a large animal in this lake.

I've caught halibut, 300 pounds,

and had sharks on that were 500 pounds,

and they wouldn't do damage like that.

I was reluctant to believe this myth

until I saw the damage

that this did to the long line gear.

And that-that kind of changed my mind.

STIGAR: I believe this is truly a fish of some sort

or some sort of animal that has gills.

It stays underwater.

It's not a whale. This animal, whatever it is,

it will dive, and nobody'll see it again.

I tend to lean towards the sleeper shark

or something similar to that.

And so, some of us just want to see what we can do

to solve some of those mysteries.

SHATNER: Ever since mankind has taken to the high seas

and explored the lakes and waterways of our world,

there have been tales of terrifying aquatic monsters.

Yet, every now and then, these terrors of the deep

aren't spotted in the open water,

but instead, found washed up on the shore.

These mysterious and often grotesque carcasses are called

unidentified sea objects.

An unidentified sea object is when something

washes ashore, a carcass of some form,

usually in a shapeless blob of blubber.

In the early days, these were called globsters.

People would just simply ignore them, move on, avoid them.

But over the years, people took more interest in globsters

as possible evidence of unknown species washing up on the shore.

Now, so many of these have washed up.

Begging the question of are they something

out of the ordinary

or something that we can simply explain?

SHATNER: Perhaps the most famous unidentified sea object

was discovered on the shore of Long Island, New York

in July of 2008.

It's a strange creature that has come to be known

as the Montauk Monster.

The Montauk Monster had a large body with four legs,

and its face was rather horrifying.

It had sharp, protruding teeth and what looked like a beak.

This thing has never definitively been identified,

fueling all sorts of speculation as to what this thing could be.

But there's countless other cases

of unidentified sea objects.

The St. Augustine Monster from 1896,

the Roch Ness Monster, 2015.

With all of these things washing up onshore,

it leads to the obvious question:

what unknown creatures may we yet find?

It's just a mystery that's waiting to be solved.

SHATNER: About 70% of our planet's covered in water,

yet we've only been able to explore a fraction

of our oceans, rivers, and lakes.

What might we find in our underwater world?

Could there be dangerous creatures of the deep

we have yet to discover?

The oceans are teeming with life,

and there are over a million species,

two-thirds of which have not been discovered

or not fully described.

The largest species on Earth are found in the ocean.

And it's impossible to say that there aren't large animals

that haven't been found.

OCKER: The oceans are this massive part of the planet.

They're deep and dark, and yet,

we have no real access to them as people.

It's an inhospitable atmosphere.

We know there are giant creatures down there,

strange-looking creatures.

And yet, all we see is this surface, right,

which can be flat, choppy, wavy, whatever it is.

But everything it has, all of its mysteries,

are all hidden below the water.

When looking at the strange and unknown creatures

that have been hiding deep underwater, you have to wonder,

could the sea monsters of myth and legends also be real?

Could the mighty megalodon

still be lurking beneath the waves?

And what about the bizarre-looking ningyo?

Are they all hiding somewhere in the murky depths?

The fact is that the vast oceans of our planet

are an excellent place for creatures of all types

to remain safely out of sight.

And until they surface, the mystery surrounding

these terrors of the deep will remain unexplained.

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