Original subtitles

NARRATOR: Sunken continents said to have once been home

to advanced civilizations.

An ancient shipwreck

containing what might be evidence of Atlantis.

And unidentified submersible objects

moving through our oceans.

For more than a decade, Ancient Aliens

has traveled the globe to investigate

some of the most puzzling discoveries

made in the depths of our oceans.

Now we're exploring

the top ten mysteries of the deep

that just may hold the proof

that Earth has been visited by extraterrestrials.

The ocean is the most mysterious place on Earth.

It covers 70% of our planet,

but less than 10% of it has been explored.

In fact, we know more about the surface of Mars

than we do about the bottom of our own oceans.

But what we have discovered in the depths

is a treasure trove of evidence

for the ancient astronaut theory.

Like an incredible underwater formation

that was found off the coast of Japan in the 1980s.

Number ten on our countdown

of the top ten mysteries of the deep:

The Yonaguni Monument.

NARRATOR: In the Pacific Ocean,

at the westernmost tip of the Japanese archipelago,

lies the small island of Yonaguni.

In 1987, in nearby waters,

dive tour operator Kihachiro Aratake

made a shocking discovery.

He found a massive complex of stone formations

that lay hidden a mere 60 feet beneath the ocean's surface.

ROBERT SCHOCH: It's an absolutely incredible structure.

It looks like a giant staircase.

There are steps in the bedrock with terraces.

The symmetry and the regularity that people see on it

just makes a astounding impression.

HUGH NEWMAN: It looks like a huge, multifaceted pyramid platform

that stretches over a huge area

with all these details carved into it.

There's areas where monoliths were said to have been standing.

There's even dolmens, or large slabs like lintels

covering areas and creating doorways and other features.

NARRATOR: Although some researchers suggest

that the so-called Yonaguni Monument

is simply a rock formation,

many experts, including Japanese archeologist

Masaaki Kimura, have come to believe

it is an artificial structure

that was built in the distant past.

(speaking Japanese)

TRANSLATOR: There are several reasons why

I think this is not a natural formation.

A number of tools and numerous engraved stones

were found at the site.

Because of these things, there is no doubt to me

that this was made artificially.

TSOUKALOS: There are all these different cuts that seem to be

of artificial origin and not of a natural origin...

...because it's too precise.

Was Yonaguni artificially altered at a time

when the water levels of the oceans were lower?

We know that this happened at some point

during the last ice age, which was 14,000 years ago.

NARRATOR: Could this massive underwater structure

really be the remnants of an advanced civilization

that existed here on Earth more than 10,000 years ago?

And if so, who built it?

ROB SIMONE: The Yonaguni Monument is particularly interesting

because some of the reports suggest that

this was built 20,000 years ago.

So the question is how was it built

with this limited ability of these people

that were known to have exist in that time?

If they had extraterrestrial help,

it would solve a lot of problems

in trying to understand how a civilization

could mount such a daunting enterprise

without what we see are the necessary skills to do so.

NARRATOR: Was Yonaguni built thousands of years ago

with the help of extraterrestrial beings?

Perhaps clues about its construction

can be found in the mythology of Japan's royal family.

It was said in ancient Japan,

that the dragon god lived at the bottom of the ocean.

His daughter had a daughter,

and her child was Jimmu, the first emperor of Japan.

To be descended from a dragon

is to be from the divine dimension of nature,

but also from the stars.

DAVID CHILDRESS: When these underwater structures of Yonaguni were found,

the Japanese became thrilled.

They believed that evidence for extraterrestrials

was right there in southern Japan.

To me, the Yonaguni Monument presents clear evidence

that an advanced society existed on Earth

long before our earliest recorded history.

And, in fact, numerous ancient cultures

around the world tell similar stories of lost civilizations,

including one that ended up submerged beneath the sea.

Number nine on our countdown

of the top ten mysteries of the deep:

The Lost Continent of Mu.

NARRATOR: The Pacific Ocean.

This body of water is the largest on Earth,

covering more than 63 million square miles.

Curiously, many ancient peoples

living throughout this vast expanse

share the same story

of a long-lost sunken civilization

often referred to as Lemuria, or Mu.

Mu was this huge continent

that supposedly existed

from Hawaii in the north,

down to Easter Island in the southeast,

right the way across to Micronesia in the west.

It thrived perhaps 50,000 years ago,

and was sunk beneath the waves,

possibly at the end of the last ice age.

NARRATOR: Among the many legends expressed by Polynesians

and native Hawaiians,

one is that the lost continent of Mu

was home to visitors from the Pleiades.

We have all kind of connection with the Pleiades,

but we call it, uh, ka po'e o ka lani,

"the people of the heaven."

WILLIAM HENRY: The Hawaiians believed that the Hawaiian Islands

were originally part of Mu,

and the belief is that the Pleiadeans

were the original settlers of Mu.

NARRATOR: While most mainstream scholars

dismiss the stories of Mu

as being little more than a fanciful myth,

ancient astronaut theorists claim that remnants of Mu

can still be found today

in the mysterious ruins of Nan Madol.

Nan Madol is a huge basalt city

that sits on the edge

of the island of Pohnpei

in Micronesia in the Pacific Ocean.

It's made up of hundreds of thousands,

potentially millions, of these huge basalt columns,

and much of the site

is still submerged in the water,

suggesting it must have been built

many thousands of years ago.

SCHOCH: Some people actually suggested that maybe Nan Madol

was the last remnant of Mu

that was still above water,

and it was simply indicative

of what had sunk beneath the waves

from this advanced civilization.

NARRATOR: Could it be that the structures on Nan Madol

are ruins of an ancient extraterrestrial civilization

known as Mu?

According to Rufino Mauricio,

the Director of the Federal States of Micronesia

Office of National Archives, it's a distinct possibility.

Legends of lost civilizations and sunken cities

can be found in cultures all around the world.

But one has captured the public's imagination

more than any other.

And some believe we may have found

evidence of its existence in the Bermuda Triangle.

Number eight on our top ten mysteries of the deep:

Atlantis.

NARRATOR: For over 2,000 years,

the lost continent of Atlantis

has sparked the imaginations of historians and explorers.

The first reference of Atlantis that we have

is in Plato's dialogues by Timaeus and Critias.

In the very end of Timaeus, it talks about

this mythical place called Atlantis

from where any and all knowledge of the world came.

And so, some people have suggested

that the first civilization on Earth may have been Atlantean.

CHILDRESS: According to legend,

Atlantis was founded by the god Poseidon.

He fell in love with a human woman named Cleito,

and they had five sets of twins.

And these twins went on to be the founders of Atlantis.

YOUNG: Atlantis is thought to be

a great civilization of high culture

and technological achievement.

They had robotics at a very advanced level.

The power of levitation, which is how

they built their glorious cities.

They had achieved things

that we still are not able to do.

NARRATOR: According to Plato,

Atlantis was destroyed in a single night

by a cataclysmic flood,

which some identify as the Great Flood

described in the Bible.

But where the famous city was located remains a mystery.

Atlantis was allegedly this land mass that existed

beyond the Pillars of Hercules,

which is today's Strait of Gibraltar,

and to this day, if Atlantis existed,

we have no idea where exactly Atlantis was.

NARRATOR: While most mainstream historians

dismiss the story of the sunken civilization

of Atlantis as a myth,

ancient astronaut theorists believe it really existed.

And as evidence, they point to a remarkable discovery

made off the coast of Cuba.

Canadian explorer Paulina Zelitsky and her team

are conducting an oceanic survey off the coast

when they detect curious formations

more than 2,000 feet underwater.

PAULINA ZELITSKY: I was in control room on board of the ship.

There suddenly appeared

a very large, very dark images

of, uh, perfect geographical shapes.

NEWMAN: They found, when they were taking images,

some kind of pyramidical structure

and other structures.

There were circular areas,

there was what appeared to be

some kind of city built down there.

It was about two square kilometers in size.

And so, this is something quite astonishing

if this is, you know, a reality.

COLLINS: And almost certainly,

this dates back several thousand years,

and arguably even earlier,

and is part of a lost civilization.

NARRATOR: Is it possible that the underwater ruins

off the coast of Cuba are the actual remains of Atlantis?

Ancient astronaut theorists say yes,

and as further evidence,

they point to their location near the Bermuda Triangle,

a region notorious for mysterious lights,

strange disappearances

and unexplained phenomena.

CHILDRESS: It's speculated that in Atlantis,

they were creating huge pyramids and energy devices.

The idea is that there is still one of these pyramids,

and it's active beneath the Bermuda Triangle

on the ocean floor,

and it's creating these anomalies

that are sometimes seen there at the Bermuda Triangle.

If you are a researcher into Atlantis,

this is exactly the kind of discovery

that you are looking for.

Some kind of pyramid that's underwater.

And in fact, this may well be,

really, the evidence for Atlantis that we need.

Did Atlantis really exist?

Recently, a mysterious metal alloy was recovered

from the depths of the ocean

that may offer further evidence.

Number seven on our countdown:

Orichalcum.

NARRATOR: Sicily. 2015.

Archaeologist Sebastiano Tusa

excavates a shipwreck less than a mile off the coast,

which has remained undisturbed for more than 2,600 years.

His team dredges up an ancient payload

of 39 metal ingots.

Spectrographic analysis of the recovered alloy

reveals the compound is unlike anything

ever found in the ancient

or modern world.

The interesting part about this

is the composition of the ingots that they found.

The metal is 80% copper, and 20% zinc.

There was other things found in it,

but that's the majority of the composition.

What's interesting about this

is that zinc doesn't naturally occur.

We didn't have zinc until about a thousand years ago,

and this is 2,600 years old.

NARRATOR: How is it possible that such an advanced alloy

was produced thousands of years ago,

centuries before man had the technology to create it?

After conducting an analysis,

scientists believe the mysterious alloy

is orichalcum, a metal associated

with the legendary continent of Atlantis.

CHILDRESS: According to Plato,

orichalcum was an orangish gold-type metal

that was used in Atlantis.

It's thought that orichalcum

was some kind of alloy of copper and gold,

and the walls of Atlantis were wallpapered,

literally, with this reddish-gold metal.

NARRATOR: According to Plato,

this metal was given to the people of Atlantis

by the Greek god Cadmus.

JASON MARTELL: The actual discovery of the orichalcum metal

lends credence to the idea that Cadmus

did exist at one time,

passing this knowledge to humanity.

And Atlantis could be an actual physical location,

possibly harnessing and utilizing other advanced metals.

The reason why this ties in to the ancient astronaut theory

is based on an idea

that the ancient gods of Greece

were visiting extraterrestrials.

NARRATOR: Could this mysterious metal,

found deep beneath the ocean's surface,

be proof that humans lived side by side

with otherworldly beings thousands of years ago?

Ancient astronaut theorists say yes,

and suggest that further evidence

of extraterrestrial contact can be found submerged

in the waters off the coast of India.

India is a treasure trove

for the ancient astronaut theory.

Its mythology is chock-full of stories of flying chariots

and god-like beings descending from the sky.

And every so often, the ocean offers us evidence

that these stories could be true.

At number six on our list

of the top ten mysteries of the deep:

The Lost Pagodas of Mahabalipuram.

NARRATOR: Mahabalipuram, India.

On December 26, 2004,

a powerful tsunami

caused the water levels in the city's harbor to drop.

As the waters receded,

residents noticed something astonishing

emerging from the sea:

the ruins of several ancient buildings.

SCHOCH: The ocean receded about 500 or so meters,

and people that were there,

they said they saw walls, they saw structures

that they'd never seen before 'cause now the water was gone.

NARRATOR: For the more than one billion Hindus

around the world,

the discovery of these underwater ruins

was remarkable because they may provide evidence

that a sensational story

contained in ancient sacred texts called the Puranas

is not mythological but historical.

According to the story, thousands of years ago,

seven pagodas stood at Mahabalipuram,

but six of them became submerged beneath the sea

after the city was attacked by a god

who came down from the sky.

CHILDRESS: The legend at Mahabalipuram

says that the god Indra became jealous

of the special treatment of the other gods depicted at the site.

And that he then sent a flood against the city.

Hindu mythology really reads like

the wildest science fiction of today.

It's filled with all kinds of magic stones,

flying spaceships.

TSOUKALOS: In fact, ancient India,

their entire pantheon of gods is based

exclusively on a cosmic origin,

that they arrived from deep space.

NARRATOR: For centuries, many Hindus believed

that the Shore Temple at Mahabalipuram

represented the one surviving pagoda from Indra's attack.

Could the structures that were revealed

by the receding ocean levels in 2004

be the remnants of the other six pagodas,

proving that the incredible story is true?

CHILDRESS: At Mahabalipuram, you have evidence that the legends

are really correct about this place.

That it's far more ancient than archeologists assumed.

And it would seem to be an indication

that this was a real event,

one that perhaps included extraterrestrials.

If you leave Mahabalipuram

and travel 1,000 miles northwest,

you will find another mysterious site

off the coast of India.

20 feet beneath the waves are the ruins of an ancient city

that some believe was the home of an extraterrestrial being.

Number five on our list:

The Sunken City of Dwarka.

NARRATOR: Dwarka, northwest India.

April 1983.

Marine archeologist Dr. S.R. Rao

begins a seven-year underwater exploration

just off the coast of this ancient fishing town,

and what he finds is stunning.

Submerged 20 feet beneath the surface of the ocean,

he finds sandstone walls, cobblestone streets,

and further evidence of a prosperous ancient city

that sank into the sea.

At Dwarka, what has been found so far under the ocean

is incredibly tantalizing.

For instance, there's this huge wall,

estimated about 580 meters long.

Pottery has been found, anchors have been found,

so this seems to have been a maritime city.

COLLINS: The remains that have been discovered beneath the waters

have been radiocarbon dated

to at least 9,500 years.

So, this was many thousands of years

older than that of Sumeria,

Egypt and China.

So, what exactly was going on

in India at this time?

NARRATOR: For centuries,

the modern-day city of Dwarka

was thought by many Hindus

to be the Dwarka described in the Mahabharata

as the ancient kingdom of the god Krishna.

According to the text, during the Kurukshetra war,

a rival to Krishna, Lord Salva,

attacked Dwarka from a flying chariot.

He actually, uh, flew over Dwarka,

using his chariot,

and he started bombarding the city of Dwarka,

throwing down all kinds of weapons.

Shortly after the great war, Krishna is killed.

And the city, this magnificent city

built on land that came out of the sea,

sank back into the ocean again.

It only existed during the time that Krishna lived there.

COLLINS: Is it possible

that the pre-Vedic cultures of India

really did have high technology?

And I think, from the ancient accounts

and what's now been discovered at Dwarka,

the answer has to be yes.

The discoveries at Dwarka and Mahabalipuram

provide sensational evidence that ancient Hindu stories

of advanced technology are not works of fiction.

And there is yet another incredible underwater structure

located between India and Sri Lanka

that may offer further proof.

Number four on our list:

Rama's Bridge.

NARRATOR: Just off the southeastern tip of India lies Sri Lanka.

This island nation has been an important trading hub

for thousands of years,

but it is nearly impossible

for ships to pass between Sri Lanka and India

due to a more than 30-mile-long underwater barrier

that links the two landmasses.

TSOUKALOS: If you look at satellite imagery, you can see

that there seems to be some sort of a connector, a road.

This is referred to as Rama's Bridge.

NARRATOR: The mainstream viewpoint is that Rama's Bridge

is a chain of natural limestone shoals.

But millions of Hindus believe the barrier is,

in fact, an ancient bridge,

one that was built by the god for whom it is named.

Rama is a major Hindu deity,

considered by some to be the supreme being.

According to the ancient Sanskrit text the Ramayana,

Rama's wife was kidnapped and taken to the kingdom of Lanka.

To rescue her, Rama used magical construction techniques

to build a bridge to Lanka.

Some of the interesting details of the building of Rama's Bridge

is that they were writing Rama's name on these stones

and that would magically levitate the stones.

And some of these were very big stones, too.

SHIMKHADA: According to the mythology,

you know, Rama lived around 6,000 years ago,

and there is interesting fact that some geologists

carbon-date the material on the bottom

approximately dating around the same time.

So that kind of corroborates whether or not

this story is connected to the mythology

because the age of Rama is around that period.

NARRATOR: In 2018, government officials in India

voted against plans to cut a shipping lane

through the middle of the barrier,

showing their support for the notion

that the underwater structure known as Rama's Bridge

was, in fact, built by the Hindu deity.

CHILDRESS: Rama's Bridge to Sri Lanka is real.

And you have to ask yourself, was it built

artificially by levitating stones and putting them there?

That's what the Ramayana tells us.

Some of the mysteries we've investigated

on Ancient Aliens are so baffling,

we can only guess at what might explain them.

And perhaps one of the most mystifying

lies on the islands of Malta.

Number three on our countdown

of the top ten mysteries of the deep:

The Malta Cart Ruts.

NARRATOR: In the middle of the Mediterranean Sea,

just south of Sicily, lies the Republic of Malta.

This tiny island nation

boasts some of the most impressive megalithic structures

on the planet.

And crisscrossing the islands

is something even more mysterious:

a complex network of grooves carved into the bedrock

known simply as the "cart ruts."

SCHOCH: Something that Malta

is very well known for archaeologically,

besides the megalithic temples,

are the cart ruts.

These are ruts literally in the limestone rock.

TSOUKALOS: If you have grooves

that were created by some sort of a transportation device,

well, it had to have been pulled by something,

so where are the footprints?

There are no footprints.

NARRATOR: How and why the cart ruts were formed remains a mystery,

but their existence poses a profound possibility,

because some believe

they may reveal that there was human activity on Malta

many thousands of years before

what has been suggested by mainstream archaeology.

TSOUKALOS: We have cart ruts

that go into the Mediterranean Sea.

And then they also come out on the other side.

How is this possible?

NARRATOR: Some of the cart ruts that extend from dry land

down into the sea have reportedly been found

at depths of as much as 140 feet.

This presents a critical clue

as to just how long ago they must have been created.

I suspect that some of these cart ruts are really ancient,

and when I say "really ancient,"

that is going back

to before the end of the last ice age.

So, approximately, uh, 12,000 years or so,

the ice age ended, we know.

Some of these cart ruts going into the water,

that would've been dry land when sea levels were much lower.

If you propose the idea that 12,000 years ago,

which is a fact, the worldwide water levels were lower,

then all of a sudden, these cart ruts

that go into the Mediterranean Sea make sense.

The fact that these cart ruts exist,

to me, illustrates that an advanced civilization

must have existed at that time.

NARRATOR: If the cart ruts are more than 12,000 years old,

as some researchers suggest,

who would have been around to create them?

It's a question that continues to baffle

mainstream archaeologists.

But according to local traditions,

the megalithic structures on Malta

were built by a race of giant beings

who came to Earth from the stars.

HENRY: We have to be open to the possibility

that whoever built these

were not, in fact, human beings,

but were perhaps a separate race,

and their existence and even their origins,

is completely shrouded in mystery.

NARRATOR: Are the so-called "cart ruts,"

that not only crisscross Malta

but extend deep into the Mediterranean Sea,

evidence of advanced, otherworldly visitors?

For ancient astronaut theorists,

the answer is a resounding yes.

And they suggest that the waters of our oceans

not only contain evidence

of extraterrestrial visitation in the distant past,

but they are the location of encounters

that are happening to this very day.

Most people assume that UFOs are only seen up in the sky.

But what if I told you that some of the most

widely reported sightings involve mysterious craft

flying in and out of our oceans?

Number two on our countdown

of the top ten mysteries of the deep:

Unidentified Submersible Objects.

NARRATOR: Hitachi Province, Japan.

1803.

Local fishermen are astonished when a mysterious metal craft

washes ashore that is unlike anything they have ever seen.

NICK POPE: This craft was likened

to the shape of a Japanese incense burner.

It is almost literally a flying disk, a flying saucer.

On the outside of this craft

were multiple small metal plates,

not too dissimilar to heat-resistant tiles

that you'd find, say, on a space shuttle.

NICK REDFERN: A hatch opened,

and a young woman came out of the craft

dressed in clothes that had never been seen before,

and speaking a language

that nobody understood in the slightest.

POPE: The story of the strange craft

appears in three different Japanese texts.

Even today, modern historians

struggle to understand what this means.

NARRATOR: Another famous incident

involving a strange craft emerging from underwater

occurred in Yunnan Province, China,

on October 24, 1991.

A local man was fishing on Fuxian Lake

on a clear and tranquil day

when a large disc suddenly flew out of the water.

POPE: This strange craft

actually emerged from the waters of the lake.

He described it as a shining disc.

This UFO was so close and so powerful

that it actually tossed the boat around.

And then, rapidly, this craft

just disappeared up into the sky.

NARRATOR: Navy personnel aboard the USS Omaha

capture footage of a mysterious round object

flying into the ocean.

TAYLOR: Night footage

actually shows a craft

that is spherical and it's flying through the air...

...and then suddenly it flies into the water

without making a splash.

NARRATOR: Japan. China.

San Diego.

These are just three out of hundreds of reports

of what are known as "USOs."

BILL BIRNES: A USO is an "unidentified submerged object."

It's the same thing as a UFO,

except this one's in the water,

and a UFO is a flying object.

You see them off the coast of California,

you see them a lot in the Gulf of Mexico.

Spend some time on the Florida Gulf Coast,

you will see a USO.

TAYLOR: These objects are flying along,

uh, through the atmosphere,

and then suddenly, they go into the ocean.

No splash, no wake, nothing.

They just go right into the water

and then come out of the water in many cases, and fly away.

Now, one such never came out of the water,

and a submarine was actually dispatched to look for a craft

that may have crashed, but never found anything.

KAKU: The stresses and strains

by flying through the atmosphere,

in outer space and then plunging into the oceans

would be enough to rupture any of our known aircraft.

NARRATOR: For ancient astronaut theorists,

perhaps the most compelling story

of an extraterrestrial presence in Earth's oceans

can be found in an account

from 1492,

recorded by Christopher Columbus.

There's a famous story about Christopher Columbus

and he wrote this in his journals...

...that as he was moving west across the Atlantic,

towards the Caribbean, in his first voyage,

he saw a light out in the ocean to the west,

hovering over the water.

And this light then descended into the water.

So, he's perhaps one of the first witnesses to describe

a trans-medium craft like this,

which could hover, uh, above the water

and then disappear into it like a submarine.

BIRNES: Stories of undersea objects, glowing objects

that fly out of the water, have been around

for well over thousands of years.

Are these machines that the extraterrestrials

have under the water?

There is only one mystery left on our countdown,

and you don't want to miss it because what was discovered

just may be evidence of an underwater alien base.

On Ancient Aliens, we've investigated

the ocean's biggest mysteries

for evidence of extraterrestrial contact in the distant past.

But recent satellite images

may suggest that otherworldly beings

are inhabiting our oceans today.

Number one on our list

of the top ten mysteries of the deep:

Underwater Alien Bases.

NARRATOR: With almost 200 miles of coastline,

this picturesque region is famous for its beaches,

surfing and abundant sea life.

It is also a hotspot

for sightings of mysterious lights in the water.

BIRNES: Folks have seen lights

in the water outside Point Dume

off the Malibu coast.

There is this very strange 911 call

from an observer near Point Dume,

saying he saw a light coming out of the water

and calling it into the sheriff's station.

POPE: One theory about this trans-medium travel

and these USOs is that what we're seeing

is evidence of underwater bases.

They're operating here, but under the oceans,

right under our noses.

NARRATOR: While the idea of underwater alien bases

in Earth's oceans may sound like science fiction,

in 2014, satellite imagery

revealed a very curious formation on the seabed

six miles off the coast of Malibu.

CHILDRESS: The satellite photos show what seems to be

an oval, flat-topped structure

that's got legs coming down that are holding it up.

It's about 2,000 feet underwater.

POPE: A lot of people got very excited by this discovery.

It's really quite striking,

and it really does look artificial.

And it makes you wonder, is this,

as some believe, an extraterrestrial base?

NARRATOR: Is there a connection between the strange lights

seen in the waters off the coast of Southern California

and the mysterious undersea structure

captured in the satellite image?

For some scientists, it's a distinct possibility.

KAKU: If all these objects are buzzing our aircraft,

they must have a base of operations.

But you see, if they have a base of operations

that's easily detected by us humans,

it would sort of defeat the purpose of observing us.

So, perhaps there's an underwater base

that is away from prying eyes of humans

so that we don't interfere with their plans.

That cannot be ruled out.

NARRATOR: While the formation discovered deep in the ocean

off the coast of Malibu is highly unusual,

it is not entirely unique.

Across the globe, mysterious anomalies

have been detected on the seabed

that some suggest are underwater alien structures.

The under ocean geological survey

determined that there were dome-like structures

between Cuba and the coast of Florida.

Was that a USO base?

Because underwater, underneath our oceans,

best place,

the very best place to conceal yourself.

COLLINS: Absolutely anything could be hiding within

the oceans themself.

And the depths of them could hide vehicles,

could even hide bases,

uh, for hundreds, if not thousands of years.

We would not be aware of their presence.

CHILDRESS: The oceans have everything

that the crew of a ship would need to survive.

It's got plants and animals that can be harvested for food.

There's minerals and salt

that can be taken from the water.

You can even separate the hydrogen

from the oxygen in the water

to create fuels and-and air to breathe.

Everything that is necessary for life

can be found in the oceans,

and it may be that if extraterrestrials

are in our oceans, they're not just hiding there,

this may be their preferred environment.

The idea that alien bases might be hidden

on the ocean floor is incredibly thrilling.

But while much of the ocean's depths

remain impossible to explore,

ancient astronaut theorists believe

that the deeper we go,

the closer we'll get to the truth

about mankind's extraterrestrial past.

CAPTIONING PROVIDED BY A+E NETWORKS