Nazi Secrets (Full Episode) | Drain the Oceans

(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: Drining 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: Drining 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.

Drining 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.

Drining 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: Drining 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: Drining 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.

Drining 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. Drining 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.