Original subtitles

Wade: Can new discoveries finally tell us

what led to one of the biggest catastrophes on the great lakes,

the sinking of the mighty ss fitzgerald?

The highest waves were up to 25 to 30 feet,

and that was exactly the place where the fitzgerald was

and exactly the time they were there.

Wade: Could newly declassified information

explain a mysterious encounter between the u.S. Navy

and an unidentified underwater craft?

The science we have today can't explain it.

It has me boggled.

Man: That didn't just happen.

Wade: And what's making one of egypt's top diving spots

one of the most deadly in the world?

200 fatalities for a single dive site

is very, very high.

This makes it only second to everest in terms of the dangers.

♪

wade: The underwater realm is another dimension.

It's a physically hostile place

where dreams of promise...

Can sink into darkness.

I'm jeremy wade.

I'm searching the world to bring you the most iconic

and baffling underwater mysteries known to science.

Shipwrecks can't just disappear, or can they?

Wade: It's a dangerous, unexplored frontier

that swallows evidence...

We know more about the face of mars

than we do our deepest oceans.

Wade: ...Where unknown is normal,

and understanding is rare.

-- Captions by vitac -- www.Vitac.Com

captions paid for by discovery communications

♪

I've been out on boats

that have suddenly become caught in a storm.

There's nothing quite as terrifying

as the destructive power of wind, water and waves.

Sometimes, these forces can prove too much

for even the strongest craft.

In 1975, a devastating maritime disaster shocked the world,

and it still has experts baffled to this day.

But could new hydrodynamic research finally tell us

what happened to the ss edmund fitzgerald?

November 9, 1975,

freight carrier,

the ss edmund fitzgerald,

sets off on her regular 5-day journey across lake superior.

She's made more than 700 similar voyages

during her career.

The weather is calm in port,

but storm warnings have been issued

for a section of the lake along her route.

These were rough conditions for smaller boats,

but for a ship like the fitzgerald,

not something that was overly concerning.

Wade: The ship's nickname is the "mighty fitz."

at over 700 feet long,

she's a leviathan built to deal with the roughest weather,

and she has an incredibly experienced skipper at the helm.

Captain ernest mcsorley has been navigating

the great lakes for most of his life.

Tuttle: He is known for his mastery of the lakes.

You don't become a captain of the largest vessel on the lake

by not being a good captain.

He had a great reputation.

Wade: After 44 years on the great lakes,

mcsorley is set to retire in a few weeks' time.

Overnight, the fitz reports increasingly stormy weather

to the coast guard.

Schwab: The waves were increasing in height,

but the waves usually didn't affect them.

Wade: Then, at 3:30 p.M. On November 10,

the fitzgerald makes a call to a ship

traveling a few miles behind.

Mcsorley reports that the fitz has suffered some damage

and asks the other ship to stay with them

until they reach the safety of the nearest port.

He did make a request that a ship would shadow him,

which basically means that he was concerned that,

in case they did have to leave the ship,

that there would be another ship nearby.

Wade: The waves are now so high they're interfering

with the fitz's radar systems.

Mcsorley puts in another call to the ship

that's following to ask for radar plots

to help guide them into shore.

Goodman: It's clear from the communications

that the captain was concerned.

I mean, it was a big storm.

They were taking on water,

but he also felt that they could continue.

And he basically said that things were going fine,

that she was moving along like an old shoe.

But that was the last that anyone heard from the ship.

Wade: At 7:15 p.M., just 17 miles from the safety of shore,

the fitzgerald disappears from the other ship's radar.

They try to radio through to the fitz, but she's gone.

♪

the only sign of the mighty fitzgerald's existence

is two empty lifeboats.

There are no survivors and no eyewitnesses.

What was it that caused such a massive ship,

almost as long as the titanic was,

to sink in a lake, not in the ocean?

Goodman: One of the big mysteries is,

why didn't the captain send a distress call?

He would've known. He had the experience.

He'd already reported that they were bringing on water,

so it's really unusual

that there was no additional distress call.

Wade: What happened to the ss edmund fitzgerald that fateful day?

It's a mystery that has haunted the great lakes'

maritime community for half a century.

[ thunder rumbles ]

lake superior is known

for its quick and violent gale-force storms,

but captain mcsorley had weathered

many of these in his time.

The event was incredibly quick

because between the communications

and the loss of communications,

it was a very short period of time.

There was no mayday or sos call,

which is quite strange from a boat there,

but it might have happened so quickly

that nobody actually was able to get to the radio.

Wade: Crews are immediately scrambled to look for the fitzgerald,

but hampered by bad weather,

it takes 4 days before the ship is located using sonar.

She's resting on the lake bed over 500 feet down.

It's a further 6 months before remote underwater cameras

can be deployed to take a proper look.

No one can believe what they find.

Polakowski: When they found the vessel, it was split in two,

which means, usually, caused by a catastrophic event.

Wade: It's unlike anything they've seen before.

Rondeau: Initially, they thought that they would find

the entire hull intact,

but researchers knew that it had broken up.

The question is, why did that happen?

Wade: For nearly half a century, no one has known for sure

what caused this mighty titan

of the great lakes to break in half,

but can new research finally tell us

what happened that fateful night?

♪

wade: In November 1975,

lake superior's largest freighter,

the ss edmund fitzgerald, vanishes with all her crew.

Those who find her wreck are shocked by what they see.

From the remains at the bottom of the lake,

it appears she's broken in two.

Now, more than 40 years later,

experts may be about to solve the mystery

of what sank the fitzgerald.

Lake superior reaches depths of over 1,300 feet,

but lurking just below the surface are natural ridges

that are catastrophic for any ship that comes too close.

There's a question of whether the fitzgerald struck bottom

going over some of the shoals near caribou island,

north of where it sank.

Wade: With his navigational tools wiped out,

could the captain have smashed his ship on the shoals?

I highly doubt a captain of mcsorley's experience

would have issues not knowing where shoals are.

Wade: The official investigation blames

the ship's failed hatch covers.

The edmund fitzgerald had 26,000 tons of ore in it.

Therefore, she's going to be low in the water,

and if you have waves washing over the deck,

they should wash off.

If your hatch covers aren't dogged down properly,

it's going to let water in.

Wade: But not all experts are convinced by the hatch theory.

I don't really believe in that because of the size of the ship.

You would have to leave them open for quite a long time.

It would be gradual.

It would have to flood slowly,

and this was a very sudden event.

Wade: What's more, the ship was equipped with two powerful

7,000-gallon-per-minute water pumps,

which were both running at the time.

What it really looked like

was that there had been a stress fracture

and that the ship had broken in two,

and then both pieces spun away from each other

and eventually sank.

Wade: Dave schwab was a rookie scientist

working on the great lakes when the fitz disappeared.

When the fitzgerald sank, no one could understand

how there could be a storm bad enough

to sink one of these great lakes freighters.

They were designed to run through the largest waves

they thought they would encounter.

Wade: But what if they came up against the most unpredictable force

that mariners can face during a storm --

rogue waves?

Schwab: Rogue waves are mysterious.

Some oceanographers like to say that it's a wave that's bigger

than 2 1/2 times the average waves that are occurring.

Wade: Also known as freak or killer waves,

rogue waves have been recorded in the great lakes,

and they can be deadly.

Rondeau: Rogue waves are an extremely real thing on the great lakes

because the water is not very deep.

A lot of people are surprised by this because they would think,

"oh, well, you only get really big waves in the ocean."

the thing that makes waves in a lake body

particularly a problem is that wave energy

has nowhere to go but up.

The great lakes are really like inland seas,

but they have these sides.

So the effects of waves and the way that waves can be produced

and produced quickly is rather different.

You can get these very, very large, very sudden waves.

It's sort of like a big bathtub.

And these waves can be changed in their shape

by the surrounding topography.

So that means that if it's close to the shore,

and there is a big wall, it can bounce off

and just create a wave with a different pattern

and make that wave grow higher.

Wade: Lake superior is legendary for a strange phenomenon

called the "three sisters."

rondeau: There's an old saying with waves that waves come in threes.

Oftentimes, the third wave can be the biggest.

Goodman: When you have rogue waves that occur one after another

after another, the ship doesn't have a chance to recover

after the first one hitting the ship,

and this can cause it to sink.

Wade: But how do we discover if rogue waves appeared on lake superior

on that day more than 40 years ago?

Oceanographer dave schwab does what nobody

has ever done before.

He converts the records of weather conditions

into a detailed hour-by-hour model.

We could estimate based on the output

from the meteorological model

what the wave conditions were at any point in time

and any point in space during those 3 days.

Wade: Schwab recreates wave heights across the lake

for every hour during the ship's tragic crossing.

We basically split the lake into a number of grid boxes.

Each of those boxes that's within the lake

is represented in the computer

as a cell that can interact with wind from the surface

and with its adjacent cells.

Wade: Can this new mapping of the water's dynamics

bring us a step closer to understanding

what happened that terrible night?

The wave model predicted that the highest waves

were occurring maybe up to 25 to 30 feet,

and that was exactly the place where the fitzgerald was

and exactly the time they were there.

Wade: And the model reveals one other crucial clue.

As the waves were growing in height,

the distance between them was also growing.

Wave crests in the area

the fitzgerald sank were becoming hundreds of feet apart.

Wade: The same length as the ss edmund fitzgerald.

So one end of the ship is on the crest of one wave.

The other end of the ship is on the crest of another wave,

and there's nothing in the middle

to hold that ship above water.

Ortiz-vazquez: If this ship was so long that it was actually riding two waves

at the same time, and it was on each peak,

then the part of the middle of the ship

would just be hanging in midair,

and that would create a lot of stress on the hull.

And if you have very big cargo, it could just split in half.

The distance between wave crests becomes longer and longer.

During this storm, I don't know whether that had some effect

on the dynamics of the buoyancy of the ship

or how it reacted to waves that long,

but these are unusually long waves for the great lakes.

Dave schwab's work offers a new and very plausible explanation

of the unique set of circumstances

that could have caused this terrible tragedy,

but until more evidence is uncovered, it remains a theory.

And our deep waters often have a way of swallowing

the evidence we need.

♪

we're used to stories of ufos spotted in our skies,

mysterious visitors from outer space,

but could there be alien craft in our oceans?

In 2004, mysterious underwater objects

are detected by u.S. Warships

on a training exercise in the pacific.

It appears that no one knows what they are.

Can newly declassified information finally reveal

the secret of what's going on beneath the surface?

November 14, navy carrier, the uss nimitz,

is 100 miles off the coast of san diego.

Reports come in of strange unidentified objects

in the water.

Four f/a-18 hornets are sent to investigate.

What they find astounds them.

The pilots observed an object in the water

roughly the size of a 747, basically right at the surface,

and the water around it seemed to be boiling or churning.

For the navy to see an object they don't recognize

is unbelievable,

but that it's acting this way is even more mysterious.

Wade: Then the pilots spot something totally incredible.

The pilots first observed the bigger object in the water,

but then they subsequently see a smaller object, about 40 foot,

come up to it, dock with it and then take off into the air.

Wade: The smaller craft suddenly starts to move erratically,

pinballing around.

The largest craft disappears into the depths,

leaving no trace.

So here we have this monster-sized

whatever thing bubbling underwater and going away.

Wade: The smaller craft shoots off through the sky

with the hornets giving chase.

They describe it as 40 feet long and shaped like a giant tic tac.

It has no wings or visible means of propulsion.

They're obviously tracking a mysterious object.

Wade: And it does something else that truly defies logic.

It plummets into the water at incredible speed.

The calculations that they made of the speed that this went

from about 20,000 feet to the surface of the sea

was in about a second, which is completely ridiculous.

Man: That didn't just happen.

That's obviously traveling faster than the speed of sound.

Where are the shock waves?

Where are the sound waves that would emanate from it

and then the physical impact of going from gas

to the other medium, liquid,

without having some kind of catastrophic failure?

Goodman: What we're seeing doesn't seem possible in terms of physics.

Wade: Missile cruiser, the uss princeton,

is also taking part in the exercise.

Her sonar picks up multiple small objects

moving through the water.

The fact that these objects are moving really,

really quickly through the water,

we simply don't see this.

Wade: The fastest submarine can reach a maximum speed

of 51 miles per hour,

but these objects are reported to be traveling

10 times that speed, over 500 miles per hour.

The science we have today can't explain it.

Has me boggled.

Evidence of this encounter remains classified

until the u.S. Military finally releases it in 2017.

What are these incredible craft

that appear to defy the laws of physics?

Is this proof of an underwater alien encounter

or something else entirely?

♪

wade: In 2017, the u.S. Navy releases evidence of an encounter

with unidentified submersible objects

traveling at extraordinary speed through the pacific ocean.

No known craft can travel that fast through water,

so what on earth could they be?

While we have planes that can achieve supersonic speeds

through air, water is 800 times more dense.

Polakowski: When objects move through an underwater environment,

there's a lot more friction along the hulls of vessels,

so they have to produce more power to be able

to push through whatever they're trying to move through.

So in water, there's more friction,

more barriers to push through, versus than in the air.

Wade: The interaction between a fluid and an object's surface

causes a phenomenon called skin friction drag.

The faster you go, the more power you need

at an exponentially increasing rate.

So for something to be going that fast through water,

it's got to be overcoming this friction.

Mckay: There are very real limits to how fast you can travel

underwater,

and these objects completely defy those limits.

Wade: Could they have come from another world?

Mckay: The first thing that came to my mind

is that this is a meteorite,

and if it were a meteorite, you would see a burning rock.

And then you'd see a gigantic splash

when it eventually hit the ocean.

There's also the option it's extraterrestrials,

which is beyond my knowledge

and beyond anyone's if they're extraterrestrial.

Wade: But there is one scientific theory that might explain

how an object could move through water at great speed

without the involvement of extraterrestrial beings.

It's a technology called supercavitation.

Clarke: This is where something is working in an air bubble,

so instead of it having the friction of water to deal with,

it's got the friction of moving through an air bubble.

And the air around it is what's interacting with the water,

so it's the friction of air on water,

which, of course, is very, very small.

So it manages to go that much faster.

Wade: Over 20 years ago,

russian scientists developed a supercavitating torpedo

said to travel six times faster than its predecessors.

The russian shkval torpedo is alleged to use supercavitation

to achieve unimaginable high speeds,

but it's never been used in combat.

So we're not really sure.

Wade: New evidence is emerging

which suggests the russian may not be the only ones

working on underwater supercavitation technology.

Recently, the u.S. Navy

have filed for several mysterious patents.

Mckay: Three of these patent are suggestive

of a high-speed aerospace underwater craft that could

potentially be capable of these kinds of speeds.

I mean, the other question is, is this patent really a patent

of something that already exists,

or is this a patent where this is the direction

that they're thinking in terms of developing future technology?

Clarke: Is it something the americans were developing

and then not admitting that they had?

Is it something someone else was developing?

We don't know, so that's what the mystery is.

Wade: The nimitz sighting happens in 2004.

The patents aren't lodged until more than a decade later,

but could they somehow be linked?

Supercavitation has never been seen.

It's never really been demonstrated,

and it's never been proven.

It is entirely a theory which we're working towards,

so if it was something man-made,

then it is technology which is yet to be admitted to the world.

Wade: But if this really is top-secret technology,

why would the u.S. Military release the footage

and publish the patents?

Mckay: These sightings are so unusual,

and they defy physics in so many ways.

And the fact that we know about it, I think,

is highly unusual, as well.

Wade: There is one possibility which could explain

the sudden release of this information.

Clarke: It could also be the u.S. Navy putting a ruse out there

to wind up and make the chinese and the russians

and everyone else spend a lot of money

on something which is impossible.

Mckay: Could this have been a function of war games?

Could one side have been toying with the other

with some new technology?

That potential exists.

Wade: So are these extraordinary sightings a glimpse

into our technological future

or evidence of extraterrestrial life

or an exercise in military deception?

The jury is still out.

♪

the ocean floor is littered with shipwrecks,

possibly as many as 3 million of them.

Many were sunk in battle or wrecked by rocks,

and there are some ships still intact on the seabed

that date back over 2,000 years.

So how could one disappear

from the bottom of the ocean overnight?

Goodman: Shipwrecks can't just disappear,

or can they?

♪

wade: I've witnessed up close the sheer size

and bulk of some sunken vessels,

and for a huge shipwreck

to suddenly vanish from the seabed seems impossible.

But is it?

Off the coast of borneo are the wrecks

of three japanese cargo ships which sank over 70 years ago.

Known as the usukan wrecks,

they become rich, artificial reefs.

On January 31, 2017,

a team of divers goes to see the wrecks,

but they've completely disappeared.

These are documented wrecks that have just gone missing.

Tuttle: People go back to look for these wrecks.

They're gone.

There's a giant hole in the seabed.

Wade: Where these huge hulks once lay, nothing but an eerie void

and a few mangled scraps of metal remain.

You would expect pieces of it to be left behind,

but to go to a known shipwreck

and to just see a depression in the sediment there

and virtually nothing left behind, that is bizarre.

Wade: Many wrecks do slowly dissolve over time

due to saltwater corrosion,

but the usukan wrecks disappeared much more suddenly.

How is that possible?

There are a number of theories about what might have happened.

One of the possible reasons that's been proposed is

that maybe it has to do with commercial fishing.

For years, shipwrecks have been disturbed

by commercial fishing practices.

Wade: Could the vast net of a deep-sea trawler

have caught on one of the wrecks

and dragged it across the seabed?

There's no fishing boat out there that's going to trawl

and move a huge battleship on the ocean floor.

Wade: Our deep oceans also have strong currents

running far beneath the surface.

Cold temperatures and high concentrations of salt

make them much denser than the surrounding water.

Clarke: We do know some currents

can carve deep forges through the ocean,

can give really deep trenches.

Wade: Ocean currents have been known

to move aircraft debris large distances,

but we're talking about three huge shipwrecks

weighing thousands of tons.

There is another force that lies beneath our ocean bed

that could be powerful enough.

Elliott: The ocean floor is very active geologically.

You only have to look at footage of the deep ocean

to know there are very strange things happening down there,

for example, vents giving off tall columns of gases.

There are underwater earthquakes and volcanoes.

We're just not normally aware of them.

Elliott: We do have equipment which monitors seismic activity

underwater around the world,

but that data doesn't show any activity

which correlates to where the ships are disappearing.

Wade: A deep-sea tremor of the magnitude necessary

to swallow these ships

would surely have been picked up by seismic monitoring,

and new evidence has come to light that deepens the mystery.

The usukan wrecks are not the only shipwrecks

to have gone missing in recent years.

This has become a widespread phenomenon.

Goodman: There's this really unusual situation happening

right now where, worldwide,

shipwrecks are seemingly disappearing.

Rondeau: Ships like hms warrior in danish waters,

the hms repulse and hms prince of wales

that were sunk in malaysia,

and the question is, what's going on here?

♪

divers revisiting the site of three sunken

japanese cargo ships discover they vanished,

and other shipwrecks across the world are going missing.

So what's going on?

Mckay: The fact that it's happening all over the world

in multiple locations

and in the numbers that we're seeing, it's a catastrophe.

Wade: Perhaps there's a clue in the type of ships

that are disappearing.

They have one thing in common.

They were all sunk in world war ii,

and fragments left at some of the sites give us further clues.

It appears that these wrecks have been taken by human hands

in search of one particular commodity.

Goodman: One of the reasons that they were disappearing

is because of the valuable metals

that are in these shipwrecks.

A shipwreck represents a literal treasure trove of metals.

Brass, copper, there is tons and tons and tons of metals

in these things.

Wade: Under international law,

these shipwrecks remain the property

of the country they came from.

In the case of the usukan wrecks,

the government had permitted a company

to do archaeological research,

but someone went a step further and removed the wrecks entirely.

This is an example of what's referred to as metal piracy.

These are people who are illegally salvaging

these shipwrecks, taking the metal, selling them,

I would presume, in the black market.

Who are these metal pirates?

We don't know what nations they normally come from,

what they're underground network is like.

Wade: Many of these shipwrecks contain something

that makes them especially valuable.

World war ii ships are one of the few remaining sources

of a particularly rare category of metal.

This metal is highly valuable because, for most of it,

it was produced before the second world war,

so it has what's referred to as the pre-nuclear signature.

We're talking about metal

that was produced prior to nuclear testing.

Wade: Decades beneath the watery depths

have protected the ships from radiation,

which metal above the surface has been exposed to.

They're called low-grade metals,

which means that they have a lower radiation value,

and they're very useful for medical use,

for technological use.

And it's also highly used in modern scientific equipment,

so there's a big demand for this kind of metal.

Wade: Metals with little or no trace of radiation

are able to produce more accurate readings

for finely tuned instruments

from geiger counters to space sensors,

so they command a very high price.

But the idea that these historic sites

are being picked apart is, for many people, abhorrent.

There are world war ii wrecks with world war ii dead on them.

War vessels with war dead on them

should be considered war graves and sacred.

Goodman: We're talking about places where people died.

We're talking about military battles,

and they're essentially a place that needs to be honored

and respected.

Wade: Can anything be done to stop the illegal salvage

before all these irreplaceable monuments are stolen?

Goodman: These are well-organized professionals.

They have to have the right equipment.

It's not cheap. They're going out there.

They're using commercial diving.

Wade: It's hard to police something that's underwater

in vast areas of ocean, but new satellite technology

could help the authorities catch the pirates in the act.

Goodman: With all the satellites that we have today,

if it's clear enough water and shallow enough,

you can even see the shipwrecks themselves from space.

They can actually monitor subtle changes

that are happening on the surface

where these shipwreck sites are

and be able to recognize if something is happening.

When you try to move something as large

as a shipwreck from the seafloor,

you're undoubtedly going to leave a large sediment plume,

and landsat can also be used to detect these sediment plumes

to give some indication of where wrecks are under threat.

These plumes would show in discoloration

or differences in water, and they could give us an idea

that the water has been disturbed.

Wade: Satellites could provide vital in helping us to monitor

these wrecks and to act quickly if we spot anything suspicious.

Technology is really our way to protect these wrecks.

It's important to remember that these are cultural heritage

artifacts that need to be preserved for everyone.

Wade: Will these technological spies in the sky

be enough to turn the tide on the mysterious metal pirates

before it's too late?

♪

I've been lucky enough to explore

some amazing underwater sites,

and among the most jaw-dropping I've visited are blue holes.

Diving these deep marine sinkholes

is like venturing into an abyss.

But what has led to one particular blue hole

being dubbed the most deadly dive site in the world?

30 miles east of mount sinai

on the coast of the egyptian red sea

lies a remarkable underwater formation

known as the blue hole of dahab.

The blue hole in dahab, egypt, is this really,

really special place.

Wade: Dahab's blue hole is a giant circular sinkhole,

a deep, vertical shaft surrounded by coral and rock.

Its pristine waters and proximity to the shore

have lured divers to it for decades.

But despite its beauty, this place holds a deadly mystery.

Clarke: The blue hole of the red sea in egypt

is one of the world's most mesmerizing

underwater phenomenon.

The trouble is it's also a death trap.

Wade: In August 2004, seasoned diver andrey nikitin embarks on his

first dahab blue hole dive with his buddy and their guide.

Knowing the challenges of the site,

he has the right gear

and has even completed several preparatory dives.

Despite all this, he never makes it out alive.

Clarke: This is an experienced diver.

He's well prepared. He's organized.

It doesn't make sense.

Wade: This isn't an isolated incident.

The dahab blue hole is estimated

to have claimed the lives of around 200 divers,

making it the world's deadliest dive site.

200 fatalities for a single dive site

is very, very high.

This makes the blue hole only second to everest

in terms of the dangers.

It's very alarming for one spot, for one popular diving spot.

Wade: Is there something lurking at the bottom

of this underwater chasm

that's luring divers down to their deaths?

Despite its beauty, the blue hole is a place

that the local bedouin tribes have long avoided

because, according to legend, it's cursed.

There's a bedouin legend of a young girl who drowned while

trying to escape an arranged marriage,

and her spirit now haunts it.

This story indicates something very strange

has been going on there for some time.

Wade: The curse of a bedouin bride,

or is there something more tangible at work here?

♪

dahab's blue hole is the world's most dangerous dive site.

The bedouin believe it may be cursed

by the ghost of a local girl who drowned there.

What is lurking in its depths

that has claimed the lives of so many divers?

There are many unseen forces in our oceans that can kill.

The red sea is home to more than 40 types of shark,

including the tiger shark,

one of the few species known to bite humans.

It also has deepwater currents

capable of pulling a diver down in the depths,

but from the evidence so far,

it doesn't seem either of these factors are responsible

for the deaths at dahab.

Could a new insight help us to understand

what makes this beautiful blue hole such a killer?

Figueroa: It's a deep dive.

You want to have training and experience,

and it's a dive that you want to have your wits about you.

Its deepest depth is about 400 feet.

The maximum depth for recreational divers is 130 feet.

Wade: Diving deep can come with a dangerous side effect,

something known as nitrogen narcosis.

Narcosis is having a high amount of nitrogen

that accumulates in your body,

and that changes your perception of what's around you.

It's very similar to being drunk.

Light-headedness, a little dizzy, you're confused.

They say it's the effect of drinking a couple martinis

on an empty stomach.

It can have a euphoric effect on the diver.

They can be afraid all of a sudden.

They can lose their orientation.

This is not something that you want to happen to you

when you're at depth.

Goodman: It doesn't matter how experienced you are.

This will impact your judgment.

It will impact your decision-making,

and it changes how you respond to things.

This can be totally lethal.

Wade: And there's another spectacular feature of the dahab blue hole

that could be involved.

Archaeologist beverly goodman experienced it firsthand

when she dived the dahab blue hole in 1997.

You're coming down the side of the coral wall.

You have this beautiful coral all around the ring,

and then you're going down in depth.

And below you, it just goes into the blue,

and it gets darker and darker.

But then this light starts coming through this large arch.

Wade: The arch is a strange feature unique to the dahab blue hole.

At a depth of approximately 170 feet,

it's a mysterious tunnel

that connects the main shaft to the open sea.

Elliott: Suddenly, you find yourself into this cavern

which link the sinkhole with the red sea.

Wade: Light reflected through the arch creates a mesmerizing

but incredibly disorientating effect.

Goodman: The arch is this incredible optical illusion.

Clarke: It is this beautiful passageway that can appear both small

and large depending on your position

thanks to the diffraction of the light going through it.

And then it opens up to this clear water

going to 1,000 meters.

Wade: It's a huge temptation for divers

to follow this passageway out to the open sea.

The dazzling underwater illusions can make it look

like an easy 30-foot swim.

In fact, it's over 80.

Judging distance underwater is quite tricky,

especially when it's clear water.

You really lose perception.

So what you think is close might not be as close as you think.

What you think is far might not be as far as you think.

Wade: Could a deadly cocktail of narcosis,

confusion and optical illusion be behind these divers' deaths?

Goodman: You're feeling really good.

You're feeling this is basically laughing gas at this point,

so you're feeling a little bit high.

You're seeing this beautiful light coming through.

You're not exactly where you're supposed to be,

but the draw of going towards that light

and going through it is really irresistible.

Being a confused diver at depth could be fatal.

Wade: Is the bedouins' ghostly girl in fact the fatal attraction

of this beautiful but deadly place?

Humans love to push the limits, and I don't know if it's humans

are attracted to these dangerous experiences.

But I think we really enjoy the spectacularness of the unknown.

♪

we still have so much to learn

about the spectacular underwater realm,

but the deadly dahab blue hole teaches us a valuable lesson.

The world beneath the waves is a different dimension

where the normal rules don't apply,

and we forget that at our peril.