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.

Stories include sightings of giant sharks, prehistoric serpents, and even

-toothed mermaids. Might these terrifying creatures be the real -life

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.

The Atlantic Ocean, 2022

Off the coast of Rhode Island, researchers from the Atlantic Shark

sweep the ocean depths with sonar, a technology that uses sound waves to

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 can 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.

There is a 50 -foot sonar ping that resembles a very large shark, which is

extraordinary. Many people online started to speculate that it was our

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 3 .5 million years ago.

Recent estimates put the shark up to about 80 feet in total length, so that's

two yellow school buses lined up front to back.

So that sonar image was pretty exciting. However, the researchers, including

myself, hypothesized that this was probably just a huge school of fish that

happened to be swimming in a shape that resembled a shark.

The image of the creature, or maybe school of fish, on the monitor

went viral. Everybody was sharing this.

And what this tells us is we are so fascinated with giant sharks and

itself that even a momentary blip on a screen is enough to send everybody into

excitement and conjecture.

While conventional wisdom tells us that the Megalodon went extinct over 3

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 the megalodon have been the

biggest apex predator of its time, but ever.

We know that because we've found the teeth.

The megalodon tooth is around 7 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,

that'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 looks like a big version of a great white shark.

But that's not necessarily true. Science is always building on itself, and this

is one more example.

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

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 pot and stealing

their catch.

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.

This was documented by a 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?

While some experts propose that the fishermen saw a whale shark, the largest

stonefish 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 miko in half.

There are photographs around of animals with really big bites in them.

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

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.

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

carnivore off the coast of Bermuda.

So in 2020, a group of researchers tagged a poor beagle shark.

Now, a poor beagle shark is a pretty large fish, between 8 and 12 feet long,

apex predator.

And then, over the course of the next month, it started going to much deeper

levels of the ocean, where poor beagle 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.

Could a creature like the mighty megalodon be stalking the seas beneath

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 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.

The Flannan Isles, Scotland, December 26, 1900.

A ship named the Hesperus arrives at the tiny rocky outcrop of Eileen Moor,

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 MacArthur, who are stationed

there as keepers of the Flannan Isles lighthouse.

In 1899, they erected a lighthouse on Eilean Mor, which is one of the Flannan

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

Eilean Mor is small, 40 acres. It's basically a rock with some grass on it

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.

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

could not put the puzzle pieces together as to what happened to these missing

light keepers.

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

Despite extensive searches and people investigating over the decades, there

no trace of them ever found.

What could have 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.

They were swept away by a giant wave.

But one of the theories is that disappearance was caused by a sea

Scotland is surrounded by water, and it is known as an area where sea monsters

were believed to roam.

Scottish folklore includes many monsters associated with the dark waters of its

rugged coast.

But perhaps the most terrifying of them all is a true massive sea serpent known

as the Kirin Kroen.

The name Kirin Kroen 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 is a frightening sort of creature.

The Kirin Kroen is gargantuan.

According to folklore, this is a creature that would make a meal out of

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.

This is a relevant story to their lives.

Many have proposed that the Kirin Kroen was responsible for the missing

lighthouse keepers. When you take into account of all the damage that was

it would have taken something with immense power.

That's exactly where they believe the Kirin Kroen came in.

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

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.

In 1918, during World War I, A German U -boat, UB85,

was navigating the waters between Ireland and Scotland when they were

And the captain of the ship, Gunther Kretsch, claimed that the reason the

sunk was because of some huge creature that rose out of the water with horns

glinting teeth.

And it damaged the boat.

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.

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 light keepers over a century ago?

The Flannans' 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

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 have been eaten.

I've never discounted 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.

The hideous, razor -toothed mermaid.

Asakuchi City, Japan.

This small coastal town is home to the serene Buddhist sanctuary known as the

Enjun 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 8th 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.

While it's unclear how or when this Ningyo mummy came to the temple, the

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 Anjuan Temple's 34th chief priest,

Kozin Kuita, is its dedicated caretaker.

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.

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 Atagatas jumped into a lake,

she sprouted a fishtail.

In Thailand, folklore describes an ancient mermaid named Savanamaka.

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

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 fishtail is often hiding multiple rows of incredibly

sharp razor -like teeth.

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

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

out.

The ningyo was sent to the Kurashiki University of Science and the Art.

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.

There's lots of puffer fish scales all over it, and some cloth and cotton

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 Zinio.

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.

The specimen found in the Injun temple is just one of many of these alleged

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 dates back to the time of the dinosaurs.

The South Pacific, April 1977.

Thirty miles off the coast of New Zealand, a Japanese fishing vessel drags

massive net nearly 1 ,000 feet under the water, hoping to fill it with tons of

macro.

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

a famous photo that you can see of it where it's hanging from the boat's

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

million years.

The plesiosaur had razor -sharp teeth in its mouth.

It could get up to 40 feet in length.

Researchers believed that it would attack its prey from underneath, from

like the great white shark.

It had an extremely powerful bite force.

It was a deadly predator.

Did Japanese fishermen discover the decayed carcass of a prehistoric

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 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

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.

The Lake Champlain monster, affectionately called Champ or Champy,

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 Mancy 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

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.

Sandra Mancy's extraordinary photograph has provided tantalizing proof of

Champ's existence for a 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 lake monster, and he's been

for a long, long time.

We see this reflected in the local native lore.

The Abenaki had a name for this creature, the Gitteskog, that was this

inhabiting the lake.

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

have even suggested that this could go much further back, related to some other

mythological creatures and native traditions.

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

lake. And ever since, hundreds of eyewitness reports of Champlain have

to accumulate.

Perhaps the most compelling recent evidence surfaced in 2024 when

Kelly Tabor, and Richard Rossi were reviewing aerial footage they shot over

Champlain and noticed that they captured something extraordinary.

We were just getting an aerial shot of the lake. The water is clear.

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 a champ. We weren't expecting anything like this.

contacted scientists with their own doctorates, and those in this field say

it has the body of a plesiosaur, and it's moving, it's swimming, and it's

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 the dinosaurs?

Murking 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.

Alaska, June 2017.

200 miles southwest of Anchorage lies the largest body of freshwater in the

state,

Lake Gileana.

At over 1 ,000 square miles, this massive lake is roughly the size of

Island. And from its southern shore, onlookers notice a strange disturbance

in the water.

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 I caught it on video.

Look right there. Look at that right there.

What is that?

There's three of them. What is it?

What you could see was a shape, and the shape was smooth and rounded.

It was very dark in color, and it kind of came out of the water and submerged

itself back under the water.

I had my binoculars, and I was glancing out to the island, and these humps

appeared, and these things were huge.

Look, Gary!

Holy!

I don't know what that is.

I thought if there was anything on the lake that could match that size.

It made your heart race a little bit.

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

What was this huge creature breaching 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.

Well, 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 before this, something like the large black fish.

Since the 1940s, there have been credible sightings of something big, 10

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.

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.

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.

We started putting these large hooks baited with a full salmon head down on

bottom of the 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

to figure out exactly what it is.

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 got some of the head.

Something's taken our bait. The 38 -pound anchor had been moved at least 50

yards. So do we want to pop them off and then reset it? You want to try doing

that? Yep. We pulled up basically a knot of the entire rope minus the anchor.

Look at all these.

And all the hooks and everything were all tangled up. The part 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 longline gear.

And that kind of changed my mind.

I believe this is truly a fish of some sort or some sort of animal that has

skills.

It stays underwater.

It's not a whale.

This animal, whatever it is, it will dive and nobody will see it again.

I tend to lean towards the sweeper 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.

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

form, usually in a shapeless blob of blubber.

In the early days, these were called globsters. People would just simply

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?

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 Rock Ness Monster, 2015.

With all of these things washing up on shore, it leaves the obvious question,

what unknown creatures may we yet find?

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

About 70 % of our planet's covered in water.

Yet we've only been able to explore a fraction of our oceans, rivers, and

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.

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,

it is.

But everything it has, all of its mysteries, are all hidden below the

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 Nenguil?

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

remain unexplained.