All language subtitles for Drain the Oceans Series 1 Part 2 Nazi Secrets 720p

(speaking in German)

NARRATOR: Hitler's
darkest secrets...

And most terrifying weapons...

Lost below the
waves, until now.

Imagine if we
could empty the oceans,
letting the water drain away

to reveal the secrets
of the sea floor.

Now we can.

Using the latest underwater
scanning technology...

Piercing the deep oceans...

And turning accurate
data into 3D images.

This time...

was Australia's most
prized warship destroyed
by a Nazi secret weapon?

What made this killer
U-boat invisible?

And how close did Hitler come
to building an atomic bomb?

(theme music plays)

Hitler's ambition was global.

As the waters of Northern
Europe drain away they reveal
evidence of the Nazis most

terrifying weapon of all.

Norway, Lake Tinn.

How did a secret
operation here destroy
a Nazi nuclear dream?

RUNAR: At the bottom,
there's this Nazi secret.

No one can be sure
about what's down there.

NARRATOR: During World War II,
Nazi scientists begin the race
to harness atomic power.

-Hitler's dream
was to develop this
bomb that could really

devastate and destroy London...

turning the war in
the blink of a second.

That was his dream.

NARRATOR: But the Nazis
need a crucial ingredient
to make an atomic bomb.

It's called heavy water.

ERIC: Heavy water was a vital
component of the attempt
of the Germans to get their

nuclear reactor to work.

It's chemically hydrogen
but it's heavier,
it's twice the weight.

NARRATOR: The world's largest
producer of heavy water
is near Lake Tinn in Norway.

Vemork Power Plant,
once the world's largest
hydro-electric power station.

It is this energy that
powers the creation of
the precious heavy water.

April the 9th, 1940.

Germany invades Norway.

-The Nazis were eager to
get control of the heavy
water at the Vemork plant,

due to the reason that they
wanted to use it as a cooling
aid in their nuclear reactor.

In 1942 at the peak of the
production here at Vemork,
they produced as much as

1,000 kilos of heavy water.

NARRATOR: Over a ton is a
big step towards building
Hitler's first nuclear reactor.

-It looked as if Germany
might well get a nuclear bomb
quickly and the Allies were

obviously very
concerned about that.

Churchill wanted the heavy
water plant to be destroyed.

NARRATOR: Vemork Power Plant
becomes a priority target for
Allied air raids and sabotage.

Damage like this eventually
forces the Nazis to safeguard
their stockpile of the

precious commodity.

February 20th, 1944.

The Nazis plan to move almost
a year's output of heavy
water by train from Vemork.

The carriages will cross
Lake Tinn by ferry.

From here the cargo will
travel to Germany, to the
site of a nuclear reactor.

Soldiers load around
40 barrels on to
railway carriages.

The hydro ferry departs...

But it never reaches
its destination.

At 10:45 in the morning
it sinks, the cargo
tumbles into the water.

27 people are rescued,
26 go down with the ferry,
mostly innocent civilians.

For decades the
hydro ferry and her
secret wartime cargo lie

hidden in the dark waters...

until now.

Fredrik Soreide is a
maritime archaeologist.

He has studied this area
for over 20 years.

FREDRIK: I'm standing on
the shores of Lake Tinn.

It's a very dramatic
lake in Norway.

It's got high mountains up
to 1,000 meters around it and
the lake is very deep so it

actually goes down
to 460 meters.

For decades this lake had a
big secret and to be able to
uncover that secret the whole

lake had to be explored.

NARRATOR: 1500 feet is too
deep for divers so Fredrik
works with an expert in

remotely operated
vehicles, Thor-Olav Sperre.

FREDRIK: So today we
have the remotely
operated vehicle.

It is used to go down to
the shipwreck so that we
can film it and also make

a lot of other interesting
documentation.

NARRATOR: They're equipping
the ROV with the latest
multi-beam sonar technology,

allowing them to probe
the darkest depths.

THOR-OLAV: Take it up and
then we can load a new
profile and then start

doing the other tests.

-Yeah.

NARRATOR: Multi-beam
sonar fires sound waves
to the lake floor.

The return signal displays
the shape and depth
of the features beneath.

-It becomes then a very
detailed image and that's
what we're looking at,

that's what we want.

NARRATOR: And Thor-Olav
knows where to look.

He's been fascinated
by the story of the lost
ferry for years and he was

one of the first
to find the wreck.

Now, he's back,
with powerful new
scanning equipment and

cameras that will finally give
him the most detailed record
of what's down there.

Eventually a ghostly
shape looms into view.

The icy depths of the
freshwater lake have preserved
the decades old secret.

-Ah, there we go,
oh there it is.

-I see the frame.
-Where are we now?
-On the starboard.

-Very nice.

-The super structure is
still standing there and
we can see a lot of things

on board still.

-Yeah. We're only 3 and
a half meters above it.

-Ah look, that's a, is
that a railway carriage?

-Yes it is, upside down.
-It's upside down.

Oh it's been thrown over.

Yeah, that's the wheels.

NARRATOR: The cargo on
these carriages was once
destined for Nazi Germany.

Instead it lies deep in the
darkness of a Norwegian lake.

But why is the ferry here?

For the very first time the
waters of Lake Tinn drain away
to reveal the true picture.

Using multi-beam sonar
data combined with cutting
edge computer graphics,

the lake's astonishing
underwater landscape
comes clearly into view.

The first clue lies in the
shape of the valley itself.

There are steep banks
which descend 1500 feet
down, to the bottom of the

one of the deepest
lakes in Europe.

As the waters of the
lake drain fully away...

the drowned ferry
is brought back into
the light of day for the

first time in
over 70 years.

First the stern of the
170-foot-long vessel,
tilting downwards.

Then the wreckage of
the railway carriages...

and the
captain's wheelhouse.

The spread of the
wreckage is firm evidence of
a catastrophic, sudden sinking.

FREDRIK: Here we can clearly
see the wreck and we can see
the wheelhouse up here and we

can see there's something
behind here. Maybe....

THOR-OLAV:
Ah the bow is probably
down in the mud.

NARRATOR: So what
wrecked the ferry?

The answer is one
of the most daring sabotage
operations of World War II.

Norwegian resistance
fighters learn about the
Nazi heavy water shipment.

They are ordered by London
to stop it at all costs.

The night before
the ferry departs,
under cover of darkness,

the saboteurs board
the vessel and place a

time bomb set to
detonate at a precise moment,

then leave the
ship to its fate.

-The saboteurs knew the
stakes couldn't be higher.

They had to stop the
transportation to Germany.

(ticking)

(explosion)

NARRATOR: Draining Lake Tinn
reveals that the ferry is
precisely targeted to sink in

the deepest part of the lake.

No Nazi diver can ever
retrieve the barrels of heavy
water from these depths but is

the ferry carrying enough
heavy water to give
Hitler an atomic bomb?

NARRATOR: Draining Lake
Tinn in Norway reveals an
infamous Nazi nuclear secret

strewn across the lake bed.

Was there enough heavy
water on board to make
the Nazis nuclear bomb

program go critical?

-After the ferry went down
there was a lot of speculation
that the heavy water on board

the hydro had been replaced
by normal water because
it was so lightly guarded.

So we wanted to go down
and take up a barrel to
prove that this was in fact

the heavy water that was
being shipped to Germany.

NARRATOR: The team have
already examined three
barrels from the depths.

-Aye aye, yes.

NARRATOR: Testing samples
taken from inside the barrels
proves that they do contain

heavy water but was
the ferry's cargo large
enough to help Hitler build

an atomic bomb?

The only way to find out
is to probe the darkness
of Lake Tinn and see how

many barrels are left.

Draining the waters
of this Norwegian lake
unlocks the answers.

Amazingly, still intact
after more than 70 years.

First, one barrel
on the deck then 2 more
spilled over the side...

then 2 others, 60 feet
from the wreck site.

That's 5 barrels visible
around the wreck.

FREDRIK: Well you
can still see numbers
on the barrels, yeah?

We believe that maybe
10 barrels floated
because they were not full,

and we have picked
up 3 barrels.

NARRATOR: With at
least 18 barrels accounted
for and using the scan data

as a guide, the
survey team can
calculate where the others are.

-We believe that most of the
other barrels are actually
on board the ferry, still,

underneath turned
over carriages.

NARRATOR: That's about
half a ton of heavy water,
enough to be a vital missing

component for the
Nazis nuclear reactor.

-After the war those
involved in the German
nuclear program said

that the loss of
the heavy water was
absolutely decisive.

It stopped their reactor
program in its tracks.

(speaking in German)

NARRATOR: Nazi secret
weapons are deployed
right across the globe,

including the Indian Ocean.

Draining the waters here,
off the coast of Western
Australia reveals

two shattered wrecks...

What appears to be a German
merchant ship and HMAS Sydney.

This mighty Australian warship
disappears in November 1941.

Will draining HMAS
Sydney uncover the
mystery of what happened in

the national disaster?

JANN: For the Australians,
the loss of the Sydney
almost became something

like a national trauma.

It was the pride of
the Australian Navy.

Not knowing about her final
resting place and the fate
of her crew puzzled

the Australians for decades.

NARRATOR: After the
war, a German captain,
Theodore Detmers,

claims to have defeated
the Sydney in battle.

Few Australians trust the
German captain's account.

He had abandoned his ship,

the Kormoran, which
was reportedly nothing
more than a cargo vessel,

and there was
no evidence of a battle.

The only way to know for
sure is to find both ships.

The vessel
Geosounder begins a
remarkable search off the

coast of Western Australia.

Equipped with new scanning
technology and supported by
the Australian government

the expedition is led by one
of the world's top wreck
hunters, David Mearns.

DAVID: The atmosphere was
very tense and very pressured.

I had to locate not just
one ship, but 2 ships.

NARRATOR: The search area
is huge but amazingly
the captain of the Kormoran

left an account containing
vital clues to where his
ship went down.

Mearns homes in on an area
125 miles off the coast.

-Oh yes.
-Oh yes.

-This is exactly what
you're looking for.

NARRATOR: After 12
days at sea, a sign.

-Here we go.
-Here's the rest.

There's the shadow, that's it.

-That's it!
-That's it.

NARRATOR: Just as
Mearns hoped, by using the
captain's account as a guide

he's found the Kormoran.

Is he close to finding
the Sydney too?

-Everything all right there.

NARRATOR: Just
4 days later the missing
warship comes into view.

-It came up on the
screen suddenly and we
knew immediately that

was the Sydney.

It was just total elation
that we had found it.

We got it.
Uh-uh, that's it.
That's HMAS Sydney.

NARRATOR: At a depth
of 1 and a half miles
it's too deep to dive,

so an ROV explores
the wreck site.

-There's something.

We're on it, it's
a gun, it's hit.

-That's the one?
Oh stop, stop right there.

-That's it.
-Wow. Oh look at that.

NARRATOR: Among the
ruins of a savage fight to the
death are chilling reminders

of this ship as a war
grave for 645 men.

But the underwater
ROV camera only gives us
glimpses of the sunken ships.

Now, by combining the
scan data with computer
generated imagery...

it's possible to drain
the Indian Ocean.

This is the HMAS Sydney,
the pride of a nation,
visible for the first time

in over 70 years.

The warship is pockmarked
by battle damage, clear
evidence of an epic

close- quarters firefight.

Now using evidence from
the seabed, it's possible
to reconstruct a remarkable

struggle between the two
lost ships and show a Nazi
secret weapon in action.

NARRATOR: Draining the
Indian Ocean reveals the
lost Australian warship,

HMAS Sydney but how did such
a powerful vessel fall victim
to an ordinary merchant ship?

The Kormoran Captain's
account offers some clues.

DETMERS: It was
November 19th, 1941.

A beautiful day
with warm sunshine.

As so often
in the Indian ocean the
visibility was perfect.

NARRATOR: Suddenly,
at 4:00pm, the two ships eye
each other on the horizon,

16 miles apart.

The Kormoran signals that it
is an innocent Dutch freighter
but as the Sydney moves

in for a closer inspection
the Kormoran prepares to
unleash its deadly secrets.

The Nazi captain knows
his only chance is to
lure the warship

into a close-quarters fight.

-I let her come closer still.

Slowly, slowly.

NARRATOR: Then the
Kormoran plays its trick.

It appears to be an unarmed
merchant vessel but in reality
the Nazi ship is packed with

the kind of deadly
technology that Q might
have created for James Bond.

JANN: The Kormoran's mission
in the Indian Ocean was
to prey on Allied shipping.

It was very much
hit-and-run tactics.

NARRATOR: Unaware of the
Kormoran's true identity,
the Sydney moves in closer.

DAVID: The two ships were
about a 1,000 meters apart,
well that's basically

point-blank range.

DETMERS: The enemy cruiser
was now coming within the
range that I considered

suitable for my guns.

I gave the order,
"decamouflage!"

The Dutch flag
was hauled down and the
German war flag ran up.

NARRATOR: According to
the rules of war, concealed
weapons are perfectly legal

but only if the ship reveals
its true colors before firing.

With the wreck of HMAS Sydney
now drained of sea water,

the first shocking
evidence caused by Kormoran's
hidden weapons can be seen

in the clear light of day.

The top of the
captain's bridge,

the command center of the
ship is missing, but why?

On the Kormoran,

hidden from view
a repurposed army
antitank gun emerges

and fires shattering the
Australian captain's bridge.

-The command structure
of the Sydney would have
been wiped out in the first

opening shot of the battle.

NARRATOR: Rapid-fire
antiaircraft guns now rise
up on hydraulic ramps,

cutting down the
Sydney's crew.

On the Sydney's main
forward gun turrets the
tops have been blown off

and there's a blast hole in
the middle of one of the guns.

What causes this?

Despite its innocent
appearance the Kormoran
carries very heavy weapons,

perfect for close
range combat.

At the push of a button,
counterweighted panels lift up
to reveal these powerful guns.

At virtually point-blank
range, their overwhelming
firepower knocks out

Sydney's forward gun turrets.

-Well it's probable that
those guns were taken out
in the first 10 seconds,

15 seconds of the action.

NARRATOR: Although caught
by surprise, the Sydney is
still able to return fire and

hits the Kormoran's engine
room, setting it ablaze.

The Nazi ship now prepares
its sledgehammer blow.

Underneath the waterline
lie 2 concealed torpedo tubes,

and there are 4
more above the water,

each hidden by a steel flap.

It takes the Kormoran's
crew just 32 seconds to
prepare and fire a torpedo.

-They inflicted a great
deal of damage very quickly
on the Australian cruiser.

Guns firing, shells exploding.

I mean it's absolute
mayhem, hell on earth.

-They were just
being wiped out.

It would have been
absolute carnage.

NARRATOR: 6:25 pm.

Confident that the Sydney
is fatally wounded and most
of the crew already dead,

the Nazi captain ceases fire.

Victory.

DETMERS: Never before in naval
history had an armed merchant
vessel defeated a cruiser in

open battle.

NARRATOR: Draining the water
away from HMAS Sydney, means
crucial evidence of what

caused its final death
blow can now be seen.

A 90-foot section of
its hull is missing.

The Kormoran's torpedoes
cause critical damage
and a huge explosion.

The Sydney's entire bow breaks
off, causing the whole ship to
plunge 1 and a half miles down

with 645 men on board.

ERIC: Sydney
disappears entirely.

There are no survivors.

It's the most serious loss in
the Australian navy's history.

Now we've found the wreck, we
know what happened and now we
have an accurate idea of what

happened to the ship.

NARRATOR: But if the Sydney
was defeated why is the German
raider also at the bottom of

the Indian Ocean?

There's a clue in the original
scans of the sea floor.

Near the wreck is evidence
of a debris field,
caused by a massive blast.

What happened to
sink the Kormoran?

The Nazi ship sails
away victorious but
it has been mortally

wounded in the battle.

JANN: With the Kormoran's
engines broken down, a huge
fire on board and a number of

mines in the hold, which were
highly explosive, Commander
Detmers had no choice

whatsoever but
to abandon ship.

NARRATOR: Hitler has
similar merchant raiders,
just like the Kormoran.

To stop the ship's many
secrets from being discovered
the crew then blow up

their own vessel.

Today, the two ships
still lie just 13 miles
apart on the seabed.

(speaking in German)

The world's
oceans hide Nazi secrets
deep underwater.

The Baltic Sea.

Draining the icy waters
here reveals a forgotten
German aircraft carrier

that never saw
battle, Graf Zeppelin.

It disappeared more
than 70 years ago.

Why is Hitler's
only aircraft carrier
lying heavily damaged

at the bottom
of the Baltic Sea?

NARRATOR: For decades, the
ultimate fate of the Nazis'
only aircraft carrier is a

mystery but then an
oil survey vessel begins
scanning the Baltic Sea.

ANDRZEJ: First of all
we came across something
that piqued our interest.

We found it using
a multi-beam sonar.

After post processing
the first measurements
indicated that it's about

260 meters long.

NARRATOR: It's the
largest wreck ever
found in the Baltic.

-Wow!
It was a really big find.

It was really spectacular.

NARRATOR: Now diver and
historian, Stephen Burke is in
the Baltic to investigate the

monster of the deep,
the Graf Zeppelin.

STEPHEN: When I first learned
about the Graf Zeppelin
nothing was known as to what

had happened to it at
the end of the War.

What happened after that
was a complete mystery.

I made it my mission to
go out and find what the
fate of the ship had been.

NARRATOR: In the darkness,

nearly 290 feet
down there are only
glimpses of the lost giant.

Timber decking on the
flight deck, massive chains
from one of the anchors.

At 850 feet long, could
its massive size be the very
reason why this mighty vessel

never played a full
part in the war?

December, 1938.
Kiel, Germany.

-Hitler loved launching
large warships, he took
great pleasure in it,

he saw them as great
national symbols.

NARRATOR: Herman Goering,
the Head of the Luftwaffe,
is master of ceremonies.

NARRATOR: The Nazis had huge
ambitions for the vessel.

More than 40 fighters,
bombers and torpedo aircraft
would have made it a

mighty war machine.

Elevators would carry
aircraft from the lower
deck up to the flight deck,

planes would
launch by catapult.

ERIC: The thought of
Stukas taking off from
an aircraft carrier,

carrying out
torpedo and dive-bombing
attacks on allied ships,

it would have
greatly strengthened
their naval position.

NARRATOR: Winston Churchill
sees the Nazi aircraft
carrier as a priority target.

-The British were
very concerned that
the Germans would complete

the Graf Zeppelin.

There was a
significant threat.

NARRATOR: But the
Nazis are slow to finish
this vast warship.

Though launched and
sea-worthy, final work is
delayed time and time again

because it needs huge amounts
of construction material.

-Contrary to
appearances Germany was
very short of resources.

She was very short of steel.

Because it was thought the
War would be short then it was
thought that the Graf Zeppelin

might not be complete
in time to take part
in the war so they had to

stop building large warships.

NARRATOR: February, 1945.

The Nazis face defeat.

-In early 1945 Admiral Doenitz
issued a scorched earth policy
which was that they were to

destroy certain key assets
to prevent them falling
into Russian hands,

and one of those assets
was the Graf Zeppelin.

NARRATOR: The Graf Zeppelin is
scuttled by a German wrecking
crew never to see battle,

but that isn't the
end of the story.

It was abandoned on
the River Oder but now it
rests 200 miles away in the

middle of the Baltic.

Why is the Graf Zeppelin here?

After the war, the
Russians seize the
vast vessel as booty.

-The Russians raised it so
they sealed the holes, they
pumped the water out and

floated the ship.

NARRATOR: Then they decided
to use the Graf Zeppelin for
a unique cold war experiment.

Stephen Burke visits the
Polish naval academy in
Gdynia to investigate.

He's working with
former Polish naval
officer Adam Olejnik.

ADAM: We have a have a
picture, a lot of damage from
different military materials.

NARRATOR: Stephen's looking
for clues to explain
the ship's final moments.

-There's less damage?
-Less damage.
-Less damage on the port side?

-Less damage, yes.
-Okay.

NARRATOR: Adam is part
of a Polish Navy team
which positively identified

the Graf Zeppelin.

-The enormity of this
vessel was a surprise.

It's hard to imagine if
you haven't seen it before.

NARRATOR: They used the mapping
technology to scan the wreck.

By using the detailed sonar
scans now, for the first
time in over 70 years,

evidence of the Graf
Zeppelin's final
moments can be seen.

Emptying the Baltic
Sea of water reveals
an incredible sight,

the 850-foot-long
drowned leviathan.

The wreck clearly
shows extensive damage
caused by explosives,

including a large
100-foot hole in the deck.

-It looked like the
result of bombing.

NARRATOR: The hole wasn't
there when the Germans
abandoned the ship,

so what caused it?

In August 1947, the Russians
want to see how much
punishment the Graf Zeppelin

could take before it sinks.

STEPHEN: So they
planted a series of bombs
inside the wreck, 2,000 kilo

bombs that are
detonated on the flight deck.

They then sent in a series
of waves of aircraft to
attack the ship with bombs,

of over 90 dropped
only 5 or 6 hit.

NARRATOR: The Soviets
have no aircraft carrier
of their own, so by bombing

the Graf Zeppelin they
learned a lot about
their potential new enemies,

the British and the Americans.

-Sinking the Graf Zeppelin
showed the Russians that
aircraft carriers were not

necessarily as easy to sink
as they might have thought.

They wanted to find out how
you sank them, and they did.

(speaking in German)

NARRATOR: Nazi secret
technology reached around the
world and draining the oceans

reveals evidence of it in
the most surprising places.

The English Channel.

The grave of a remarkable
vessel equipped with a
secret technology that

could have changed
the course of the war.

Draining the oceans here
reveals the mystery of
the Nazi U-boat U-480.

JANN: U-480, you could
call it the first stealth
submarine in history.

NARRATOR: This vessel
vanished in 1945, carrying
a lethal secret technology.

What made this killer
Nazi sub invisible?

NARRATOR: August, 1944.

The D-day landings
in France have put
Nazi Germany in peril.

JANN: In August 1944
the situation for the German
U-boats in the British Channel

was rather grim because it was
one of the best defended areas
around the British Isles.

NARRATOR: The Allies
have a highly effective
method for hunting the

submarine raiders: sonar.

Earlier in the war,
the Nazi U-boats savaged
Allied shipping in the

Battle of the Atlantic...

largely by hunting in
packs on the surface where
sonar is of limited use.

But by 1944, heavy surface
patrols force the U-boats to
operate completely underwater

making them much more
vulnerable to Allied sonar.

-This isn't wolf pack
warfare against convoys,
it's individual submarines

stalking individual ships.

INNES: Operations in a
submarine in the English
Channel at that time were

extremely dangerous.

Your chances of survival
if you're the commander of
a U-boat are about 50/50.

NARRATOR: The Nazis want to
counter the threat of sonar.

-The German answer to sonar
detection was developing some
kind of cloak of invisibility.

NARRATOR: By August
the 21st, 1944, Hitler's
designers have achieved their

dream of stealth technology.

U-boat Captain Hans
Joachim Foerster and
his crew lie in wait,

deep in the English
Channel and the Allies
never realize he is there.

-It's unprecedented, he gets
into the English Channel and
in 5 days he sinks 4 ships,

and he gets out.

It's the most devastating
patrol carried out in the
Channel up to that time.

It's quite remarkable.

NARRATOR: Will draining the
waters of the English Channel
help explain this Nazi secret?

Underwater archaeologist
Innes McCartney investigates
reports of a U-boat wreck

about 20 miles off the
coast of Southern England,
hidden 200 feet down.

-When you hit the water and
you put your hand on the down
line and you're swimming down

to the wreck you know the
sense of anticipation is,
is just truly incredible.

Your first interaction
with this completely unseen
object is can you work out

what it is?

NARRATOR: Now, for the
first time, the waters in the
English Channel drain away and

bring U-480 into the
clear light of day.

The secret of the stealth
submarine is revealed:

the entire surface
of the U boat is
covered with rubber panels.

Each panel has a series
of tiny regular holes,
instead of reflecting sonar

signals back to
an Allied warship,

these rubber
panels absorb them,

making it
effectively invisible.

-I put my hand on a, a
black rubber panel and I
was like, I don't believe

what I've just seen!

ERIC: Diminishing the
effectiveness of the other
side's sonar could well make

the difference between
life and death.

NARRATOR: Today, in
Kiel, Germany, one of U480's
sister boats still survives.

-U480 wasn't a particularly
new design, it was the basic

Type 7 U-boat
only covered with this
special cloaking device.

NARRATOR: But draining
U480 raises another
critical question: if it was

undetectable, why is
U480 at the bottom of
the English Channel?

Removing all the water means
that clues to the damage done
to U480 can now be revealed.

It has sustained
a critical blow.

The stern section is
broken off and there's a
hole in the pressure hull.

What caused such
devastating damage?

Faced with a
modern hi-tech threat,

the Allies resort to a
very old-fashioned
response:

mines.

-The trap that U480
fell victim to was
a secret minefield.

NARRATOR: February, 1945.

Shipping lanes crisscross the
channel but all Allied vessels
are secretly warned not to

travel in a specific
shipping lane area and
unknown to the U-boat crew,

the British lay what's called
a 'deep trap' minefield
far below the surface...

Then wait.

-U480 returned to what had
been its old hunting grounds,

expecting to find
some more targets.

The navigational buoys were
there so it seemed as if the
route was still being used.

In fact it wasn't.

The British were laying
minefields and these came
as a very nasty surprise.

-It was laid at
the exact point they
knew U480 was going.

Targeted killing,
based on intelligence.

That's why you keep it secret.

You're blind...

Terrifying.

(explosion)

NARRATOR: 320 pounds
of explosive bursts a
hole in the submarine,

letting in tons of
water per second.

There is no chance of escape.

The secret
stealth technology was
years ahead of its time,

but in the end
even its special
cloak of invisibility

could not save U480
from the victorious Allies.

The Nazis lost World War II.

But the deadly secrets
they left behind under
the world's oceans...

Are a reminder of the
extraordinary courage
of the men and women who

brought the Nazis down.

Captioned by Cotter
Captioning Services.