Hanging by a Thread

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0:00:02 > 0:00:06In May 1939, the crew of the submarine USS Squalus

0:00:06 > 0:00:10was struck by disaster, deep below the surface of the Atlantic Ocean.

0:00:18 > 0:00:23They were trapped on the ocean floor with their air running out and no means of escape...

0:00:24 > 0:00:29the latest victims of what the US Navy dubbed the coffin service.

0:00:42 > 0:00:48Their fate depended on one man, naval inventor Charles "Swede" Momsen.

0:00:52 > 0:00:55Momsen's attempt to rescue the men of the Squalus would become one

0:00:55 > 0:00:59of the most celebrated rescue missions in maritime history.

0:01:01 > 0:01:06It kick-started a whole new area of underwater technology and revolutionised our understanding

0:01:06 > 0:01:11of what can be achieved in the dangerous and alien world deep beneath the waves.

0:01:28 > 0:01:35On May 23rd 1939, a prototype American submarine was preparing for a routine dive.

0:01:38 > 0:01:44The exercise was taking place 25 kilometres off New Hampshire on the east coast of America.

0:01:46 > 0:01:48- Are you ready for diving, crew? - Aye, sir.

0:01:52 > 0:01:56This was the USS Squalus' 19th test dive -

0:01:56 > 0:01:59a timed crash dive for use in emergencies.

0:02:04 > 0:02:09- First officer, prepare to dive the boat!- Prepare to dive the boat!

0:02:09 > 0:02:11Under the command of Lt Oliver Naquin...

0:02:11 > 0:02:18- Dive the boat.- Dive the boat. - The Squalus had to dive to periscope depth - 15 metres - in 60 seconds.

0:02:19 > 0:02:27- Mark.- That's one, two and three, OK? - A series of levers closed the valves that fed air to the diesel engines.

0:02:27 > 0:02:32Green signalled that the sub was watertight.

0:02:34 > 0:02:36At 7.40am, the dive began.

0:02:48 > 0:02:50Mark.

0:02:50 > 0:02:5262 seconds.

0:02:52 > 0:02:53Well done, gentlemen.

0:02:56 > 0:03:03It seemed a textbook dive, but within seconds it went disastrously wrong.

0:03:04 > 0:03:05SCREAMING

0:03:21 > 0:03:26Unbelievably, water was pouring through the main induction valves in the rear of the sub.

0:03:33 > 0:03:36FRANTIC SHOUTING

0:03:38 > 0:03:40Main valve's not working!

0:03:47 > 0:03:49We've hit bottom, sir.

0:03:55 > 0:04:00Somehow, despite the all-clear on the control panel, a valve was open

0:04:00 > 0:04:03and hundreds of tonnes of water were pouring in the sub.

0:04:03 > 0:04:07They lost control of her and she went down to the bottom.

0:04:07 > 0:04:10Now I'm a professional diver and I know what it's like

0:04:10 > 0:04:14when things go wrong, but I've benefited from immediate backup.

0:04:14 > 0:04:16These men were on their own.

0:04:16 > 0:04:18What was going to happen to them?

0:04:18 > 0:04:23Bearing in mind that in the previous 20 years worldwide,

0:04:23 > 0:04:2822 subs had been lost, along with the lives of over a thousand men.

0:04:28 > 0:04:31They didn't call it the coffin service for nothing.

0:04:35 > 0:04:41In the 1930s, submariners like the crew of the Squalus were taking their lives in their hands.

0:04:43 > 0:04:47Underwater technology was in its infancy and, in the history

0:04:47 > 0:04:52of submarines, no crew had ever been rescued from the ocean depths.

0:04:52 > 0:04:58The disaster of the Squalus would become a pivotal event that would change underwater safety forever.

0:05:00 > 0:05:04Even today, flooding is a danger that terrifies every submariner

0:05:04 > 0:05:09and recruits are trained how to react to any breach of their boat.

0:05:10 > 0:05:14In this simulator, the sheer force of a wall of water pouring through

0:05:14 > 0:05:19at 14 lbs-per-square-inch pressure is a terrifying experience.

0:05:27 > 0:05:29This is really hard work

0:05:29 > 0:05:31but of course I knew it was going to happen.

0:05:31 > 0:05:36For those men on the Squalus it would just have been a sudden, tremendous shock.

0:05:36 > 0:05:39Freezing cold water under high pressure.

0:05:39 > 0:05:42We're here at the surface, but even at periscope depth

0:05:42 > 0:05:45it's twice what the pressure is at the surface

0:05:45 > 0:05:51and the water just comes pouring in under ever increasing pressure.

0:05:51 > 0:05:54It wasn't long, despite their best efforts, before

0:05:54 > 0:05:57the men in the rear of the sub were completely overwhelmed.

0:06:00 > 0:06:07Within a few minutes, water was flooding from the rear to the front of the sub.

0:06:07 > 0:06:10As men struggled desperately forwards, the crew who had already

0:06:10 > 0:06:14made it into the control room faced an agonising decision.

0:06:16 > 0:06:20Either wait for their crew mates to come through and risk the whole sub flooding,

0:06:20 > 0:06:26or shut the watertight bulkhead doors and condemn them to certain death.

0:06:31 > 0:06:34They were ordered to seal the control room.

0:06:39 > 0:06:40SCREAMING

0:06:43 > 0:06:4626 men died in those first few minutes.

0:06:46 > 0:06:5333 survivors were entombed in what was now a watery coffin stranded on the bottom of the ocean.

0:07:02 > 0:07:0789-year-old Carl Bryson is the last living survivor from the Squalus.

0:07:09 > 0:07:14Carl joined the Navy as a teenager in 1936.

0:07:14 > 0:07:16By the summer of 1939,

0:07:16 > 0:07:22he was a 22-year-old machinist's mate serving aboard his second sub.

0:07:24 > 0:07:28He was in the forward battery when the Squalus went down.

0:07:33 > 0:07:39I never really thought about dying there, that would never have crossed my mind.

0:07:39 > 0:07:43When the water first started to come in, I didn't have time to think about

0:07:43 > 0:07:46anything except how to shut the water off.

0:07:46 > 0:07:48Everybody said, "What did you think?"

0:07:48 > 0:07:52I didn't think anything except how can we stop the water from coming in?

0:07:52 > 0:07:57This is the main induction valve - all the water would have come in here.

0:07:57 > 0:08:01- Massive volumes of water pouring in this.- Tremendous volume.

0:08:01 > 0:08:04And it went into both engine rooms.

0:08:09 > 0:08:14The crew in the forward section of the Squalus had survived the initial flooding,

0:08:14 > 0:08:20but now they were trapped with only enough air to survive for 48 hours...

0:08:20 > 0:08:25and a new danger was already upon them.

0:08:25 > 0:08:28Water was seeping into the forward battery compartment,

0:08:28 > 0:08:33threatening to short-circuit the huge batteries that powered the sub's electric motors.

0:08:33 > 0:08:36This is the forward battery, of course.

0:08:36 > 0:08:38This is the battery hatch.

0:08:38 > 0:08:44Luke opened the hatch and the acid was bubbling and the caps

0:08:44 > 0:08:51on the batteries were coming out, so the battery was overheating, we were pulling several thousand amps.

0:08:55 > 0:09:01As the batteries heated to a critical level, the chief electrician shut off her power.

0:09:09 > 0:09:12Another 30 seconds, probably, and we would have had a battery explosion.

0:09:20 > 0:09:24Nobody in the battery compartment would have stayed alive,

0:09:24 > 0:09:28the people in the control room would have been lost...

0:09:29 > 0:09:36somebody may just possibly have made it out of the forward torpedo room. I doubt it.

0:09:37 > 0:09:41With no power, there was no heating,

0:09:41 > 0:09:46no light and no hope of raising the sub.

0:09:46 > 0:09:50For Captain Naquin, it was time to make a harrowing assessment.

0:09:52 > 0:09:54- Take a roll call.- Yes, Sir.

0:09:56 > 0:09:57- Bryson!- Aye, sir.

0:09:57 > 0:10:00CALLS NAMES IN ALPHABETICAL ORDER

0:10:05 > 0:10:07Aft torpedo, do you copy?

0:10:07 > 0:10:10FAINT BUZZING

0:10:12 > 0:10:15Aft torpedo, do you copy?

0:10:15 > 0:10:18FAINT BUZZING

0:10:18 > 0:10:21Forward battery, do you copy?

0:10:21 > 0:10:23FAINT BUZZING

0:10:25 > 0:10:27Forward torpedo, do you copy?

0:10:27 > 0:10:30FAINT BUZZING

0:10:33 > 0:10:40With almost half her crew dead, a dwindling air supply, no power and

0:10:40 > 0:10:44no way of reaching the surface, this was a submariner's worst nightmare.

0:10:51 > 0:10:55Ever since the sinking of the Lusitania in World War I

0:10:55 > 0:11:01by a German U-boat, naval commanders knew they needed submarines.

0:11:01 > 0:11:08But the early models produced on both sides of the Atlantic, some of which were even powered by steam,

0:11:08 > 0:11:14were often a greater danger to their own crews than enemy shipping - they were steel death traps.

0:11:17 > 0:11:23Submarine design had moved on by the '30s, but despite the image portrayed in recruitment films,

0:11:23 > 0:11:29service under water was still cramped, noisy and highly dangerous.

0:11:29 > 0:11:35The men who served in them had a reputation as mavericks, kind of naval pirates.

0:11:35 > 0:11:40It's said the admirals of the day saw these crews as expendable.

0:11:40 > 0:11:44But despite the dangers, there was pressing reasons

0:11:44 > 0:11:49why young Americans of the 1930s signed up for the coffin service.

0:11:49 > 0:11:55'Millions of Americans, men, women and children wait in the cold on bread lines, in soup kitchens.'

0:11:55 > 0:12:01The Great Depression of 1929 threw America into turmoil.

0:12:01 > 0:12:06By 1932, the economy had virtually collapsed.

0:12:06 > 0:12:11'..Construction virtually ceases, mills and factories shut down,

0:12:11 > 0:12:14'railroads come to a virtual standstill.'

0:12:14 > 0:12:16There were 15 million unemployed

0:12:16 > 0:12:21and the wealth of the average American had dropped to the level of 25 years earlier.

0:12:21 > 0:12:23- '..The ranks of the unemployed are...'- But the submarine service

0:12:23 > 0:12:28provided an escape from the hunger and uncertainty of the times.

0:12:33 > 0:12:38While the rest of the US was gripped by poverty and unemployment, young sailors were guaranteed

0:12:38 > 0:12:43roofs over their heads, three square meals a day and a weekly pay packet.

0:12:43 > 0:12:47'Here's one place where mess call means all hands on deck to stow cargo

0:12:47 > 0:12:51and there's plenty of room in the hold for seconds.

0:12:51 > 0:12:55'After this man stows his gear in his new locker, he hangs up a picture of

0:12:55 > 0:13:01'his old schoolteacher and makes himself at home in the comfortable barrack accommodation.'

0:13:01 > 0:13:07Submariners got an added bonus - an extra 25 or 30 a month in their pay.

0:13:07 > 0:13:12It was called submarine pay but this extra cash was actually danger money.

0:13:12 > 0:13:17The submarine service was still the riskiest branch of the Navy.

0:13:24 > 0:13:30For the crew of the stricken Squalus trapped on the ocean floor, things were going from bad to worse.

0:13:30 > 0:13:32MEN SHOUT

0:13:32 > 0:13:37In the forward battery of the sub, seawater was reacting with acid

0:13:37 > 0:13:41to produce poisonous chlorine gas, which was beginning to spread.

0:13:46 > 0:13:51We weren't to the point of gasping or anything like that, but, er...

0:13:51 > 0:13:56we could smell chlorine gas and that certainly was an indicator we wanted out.

0:14:00 > 0:14:02But there was no way out.

0:14:04 > 0:14:10The stricken sub was on the ocean floor at a depth of 74 metres.

0:14:10 > 0:14:16Radio communication was impossible that far down and the last message to base had been garbled.

0:14:16 > 0:14:22The sub was actually eight kilometres from where base understood her to be.

0:14:22 > 0:14:25Well and truly lost.

0:14:25 > 0:14:33The crew released a marker buoy and some rocket flares, but the chances of rescue were remote.

0:14:33 > 0:14:38Trapped in America's newest submarine, all the men could do was pray.

0:14:42 > 0:14:50In the '30s and '40s, subs built here at Portsmouth naval yard were at the forefront of submarine design

0:14:50 > 0:14:57and 20,000 men built virtually half of America's submarine fleet for World War II.

0:14:57 > 0:15:03Squalus was at the cutting edge of these developments and yet still the sea took her.

0:15:03 > 0:15:08Now the race was on to find her, but even if she was found,

0:15:08 > 0:15:11the big question remained - could those men be saved?

0:15:13 > 0:15:20The answer to that lay with one man, Lieutenant Charles Momsen, nicknamed "Swede" Momsen.

0:15:22 > 0:15:27In 1925, 14 years before the Squalus disaster,

0:15:27 > 0:15:33Momsen was a sub commander and was badly shaken by the tragic sinking of his vessel's sister submarine.

0:15:35 > 0:15:40Stranded on the bottom of the ocean, several of Momsen's friends lost their lives

0:15:40 > 0:15:43while the Navy stood by helplessly.

0:15:46 > 0:15:49Momsen was determined things had to change.

0:15:49 > 0:15:52Submarines had to become safer.

0:15:57 > 0:16:01Helen Hart Momsen is Charles Momsen's granddaughter.

0:16:01 > 0:16:07Swede Momsen is her hero and she knows his story inside out.

0:16:07 > 0:16:11He had lost friends, people he went to the naval academy with had

0:16:11 > 0:16:17been lost in submarine disasters, people that he actually knew.

0:16:17 > 0:16:22One of the men, when they opened the submarine after they salvaged it,

0:16:22 > 0:16:29his fingers were all torn to stubs because he had tried to open the hatch, which would have been

0:16:29 > 0:16:33impossible even without the water on top of it,

0:16:33 > 0:16:38but I guess people just do terrible things in their final hours

0:16:38 > 0:16:45and he was just overwhelmed because, at first he thought, "Well, it wouldn't be so bad -

0:16:45 > 0:16:49"they probably just went to sleep, they probably just died a simple death."

0:16:49 > 0:16:52But when they opened the hatch and he realised the agony they had

0:16:52 > 0:16:58gone through, he said, "It can't be this way, it just can't be this way."

0:16:58 > 0:17:02The year after the S51 went down, Momsen submitted plans to the Navy's

0:17:02 > 0:17:08bureau of construction for a device that could rescue trapped submariners.

0:17:08 > 0:17:13Over a year later, he discovered that they hadn't even been opened.

0:17:13 > 0:17:19He conceived of the notion of the bell, the rescue chamber and

0:17:19 > 0:17:22they just ignored him.

0:17:22 > 0:17:27It's always difficult to try and prove a point or make your way when

0:17:27 > 0:17:32you're going against the stream or when you're going against the brass

0:17:32 > 0:17:39and, of course, back in those days the Navy was more or less run by what they called surface admirals.

0:17:39 > 0:17:45They had all served on surface vessels and they weren't sympathetic with the submarine service,

0:17:45 > 0:17:52they saw it as a bunch of mavericks and my grandfather was the biggest maverick of all.

0:17:52 > 0:18:00Momsen lobbied the bureau to take his ideas on board, but again and again he was turned down.

0:18:00 > 0:18:06Then in 1927, another sub, the S4, was lost with all hands.

0:18:08 > 0:18:15Determined not to be thwarted by Navy bureaucracy a second time, Momsen began developing rescue ideas

0:18:15 > 0:18:18without the knowledge of his commanding officers.

0:18:18 > 0:18:2215 years before Cousteau invented the aqualung, Momsen set to work on

0:18:22 > 0:18:26something small-scale that he could design and test himself.

0:18:26 > 0:18:34A remarkable breathing device that gave submariners a chance of reaching the surface from 100m down.

0:18:34 > 0:18:41He had a plan for the Momsen lung and they gathered together pieces of

0:18:41 > 0:18:47hose and metal and inner tubes and put together the Momsen lung

0:18:47 > 0:18:50and then he tested it in a swimming pool

0:18:50 > 0:18:56and risked his own life, so it was his own money, his own life, his own time.

0:18:56 > 0:18:58'The lung resembles and works in rough principle like a gas mask.

0:18:58 > 0:19:03'Air exhaled into the device passes through soda lime which

0:19:03 > 0:19:06'removes the waste carbon dioxide and replaces it with fresh oxygen.

0:19:06 > 0:19:09'When each student has mastered the use of the lung,

0:19:09 > 0:19:12'he is then ready for the first attempt at underwater breathing.

0:19:12 > 0:19:16'The preliminary ascent is made from a very shallow level.'

0:19:19 > 0:19:21Crikey, it looks like a hot-water bottle.

0:19:21 > 0:19:24Doesn't it? It does. It does.

0:19:24 > 0:19:26OK, how does it work?

0:19:26 > 0:19:31- I met a man who actually was saved with this from the Tang.- This one?

0:19:31 > 0:19:34- Yeah, out in the Formosa Straits. - Oh, I'd better be careful with this.

0:19:34 > 0:19:38He ascended from a submarine with this.

0:19:38 > 0:19:40And this is what goes in your mouth.

0:19:40 > 0:19:42Right, that looks like a modern-day...

0:19:42 > 0:19:44- Right.- ..regulator mouthpiece.

0:19:44 > 0:19:45Hold that up.

0:19:52 > 0:19:54'Charging their lungs with oxygen, the men pass up through the escape hatch,

0:19:54 > 0:19:58'one at a time, holding securely to the

0:19:58 > 0:20:03'marker line and taking particular care to pause at the designated intervals for decompression.'

0:20:03 > 0:20:09The Momsen lung was the first truly successful underwater breathing device for a submariner.

0:20:09 > 0:20:13Filled with pure oxygen that recycled during breathing, it didn't allow you to stay

0:20:13 > 0:20:18under water for long, but it could save the life of a stranded sailor.

0:20:18 > 0:20:24'This man has safely reached the surface from a depth of 100 feet.'

0:20:27 > 0:20:34Wow. You've got the same pressure as on me, the water pushing on here, so equal pressure.

0:20:34 > 0:20:38- Right.- Fantastic. It just seems incredibly simple.

0:20:38 > 0:20:43- Yeah, it does.- I mean there's no diving gear, no diving suit.- No.

0:20:43 > 0:20:47Get that escape-hatch pressure equalised.

0:20:47 > 0:20:52- Mmm.- Open it, put this in, goggles on, make a run for it.- Right.

0:20:52 > 0:20:53Wow.

0:20:53 > 0:20:56'At the submarine base in Pearl Harbor...'

0:20:56 > 0:21:01This time the top brass couldn't ignore Momsen and, begrudgingly, they came round to his idea.

0:21:01 > 0:21:07'Under the supervision of Admiral Momsen, inventor of the famous Momsen lung, the future submariners

0:21:07 > 0:21:12- 'are ready for the 100-foot tower which holds...'- The Navy adopted the Momsen lung, as it became known.

0:21:12 > 0:21:16Thousands were ordered to equip every sub in the fleet.

0:21:18 > 0:21:24Floyd Matthews worked with Momsen, training submariners to use the lung.

0:21:24 > 0:21:27He's now 103.

0:21:27 > 0:21:33That's 100 feet, you know, we had three different positions -

0:21:33 > 0:21:38the bottom - that's 100 feet, one at 18 feet, one at 50.

0:21:38 > 0:21:42You see, we gradually worked them up to 100 feet.

0:21:42 > 0:21:45- You could do 100 foot, no problem? - Oh, yeah.

0:21:45 > 0:21:49I could jump overboard and go along the bottom.

0:21:51 > 0:21:54Yeah.

0:21:54 > 0:21:58You exhale and you just keep on going down but you've got

0:21:58 > 0:22:01to have something to breathe when you get there, though.

0:22:02 > 0:22:04You're empty.

0:22:04 > 0:22:05Yeah.

0:22:05 > 0:22:08So what are your memories of Momsen?

0:22:08 > 0:22:10He was an innovator, you know.

0:22:10 > 0:22:14The man was just nothing less than a genius

0:22:14 > 0:22:17and he could do anything, just about, yes.

0:22:22 > 0:22:26The Squalus was equipped with Momsen lungs for all its crew.

0:22:30 > 0:22:36The men had been trained how to use them, but Captain Naquin was deeply concerned.

0:22:36 > 0:22:42The Atlantic was freezing cold and the chances of getting all 33 men out were remote.

0:22:48 > 0:22:52We had planned an escape using a Momsen lung.

0:22:52 > 0:22:59We had the grease, we had the lungs, the water was cold, of course,

0:22:59 > 0:23:06and we were going to grease down and the captain had selected Greek Medeiros to be the first man out to

0:23:06 > 0:23:13let the buoy out with the line on it because we had to have a line to keep us from shooting up to the surface.

0:23:13 > 0:23:18We could have gotten...the first group could have gotten out of the boat, no question, but whether he

0:23:18 > 0:23:23could keep going or not, that was questionable.

0:23:23 > 0:23:29Anyhow, we had used up a lot of oxygen and the old man decided that

0:23:29 > 0:23:35it was safer to wait than it was to try and escape, so...he decided to wait.

0:23:40 > 0:23:47But Captain Naquin had no idea that his last location radioed back to base had been garbled.

0:23:47 > 0:23:48They were lost.

0:23:58 > 0:24:03With the Squalus now out of radio contact for several hours, a second submarine from the

0:24:03 > 0:24:07Portsmouth navy yard had been sent to her last reported position...

0:24:09 > 0:24:12not realising it was looking in the wrong place.

0:24:18 > 0:24:23There was no sign of the Squalus' marker buoy and no trace of any flares.

0:24:25 > 0:24:28The search dragged on and on.

0:24:34 > 0:24:39In the sub below, cold and hunger were taking hold.

0:24:45 > 0:24:50With surface contact long overdue, tinned food was given out to keep up morale.

0:24:57 > 0:25:00Pineapple seemed to be a favourite.

0:25:06 > 0:25:09Man, it was cold.

0:25:09 > 0:25:16Every place that you had condensation in the torpedo room from your breathing...

0:25:16 > 0:25:18a skim of ice.

0:25:21 > 0:25:25But cold and hunger weren't the only dangers.

0:25:25 > 0:25:29With every breath they took, the men were using up vital oxygen,

0:25:29 > 0:25:35and with each passing hour, the chances of survival became ever slimmer.

0:25:38 > 0:25:44Yet four hours after the Squalus went missing, nobody even knew where she was.

0:25:57 > 0:26:01Off the coast of New Hampshire, Squalus' sister ship, the Sculpin,

0:26:01 > 0:26:04was desperately searching for the downed sub.

0:26:04 > 0:26:10Finally at 12.40 on the 23rd May, the lookout spotted Squalus' marker buoy

0:26:10 > 0:26:16and inside was the telephone connected to the submarine.

0:26:18 > 0:26:20NAQUIN: 'This is the USS Squalus, over.'

0:26:22 > 0:26:24This is the USS Squalus.

0:26:24 > 0:26:26Is there anybody up there? Over.

0:26:26 > 0:26:28'USS Sculpin. Are you receiving?

0:26:28 > 0:26:29- 'Over.'- Yes...

0:26:31 > 0:26:34Hello?

0:26:34 > 0:26:37This is the USS Squalus.

0:26:37 > 0:26:42Just as Captain Naquin said a few words, a big swell came up

0:26:42 > 0:26:44and broke the cable.

0:26:44 > 0:26:46Communication was lost with the submarine,

0:26:46 > 0:26:51but the men on the top did know that some of those men were alive.

0:26:51 > 0:26:56They could do nothing to help them and the whole world was watching.

0:26:58 > 0:27:05'May 23rd 1939, the submarine Squalus lies on the ocean bottom off Portsmouth, New Hampshire.

0:27:05 > 0:27:07'59 men are trapped inside...'

0:27:07 > 0:27:13As a fleet assembled above the Squalus, the world knew there were survivors below.

0:27:13 > 0:27:15Papers rushed to print the story.

0:27:15 > 0:27:18The plight of the crew became front-page news.

0:27:20 > 0:27:24The pressure was on to do something for the men,

0:27:24 > 0:27:32but so far no crew had even been rescued from a sunken sub - it was simply too difficult a challenge.

0:27:32 > 0:27:37For wives and families waiting in the town of Portsmouth, it was an agonising time.

0:27:41 > 0:27:48The whole of the town here at Portsmouth was looking at the navy base over there for answers.

0:27:50 > 0:27:55The whole town would have just been waiting and hoping for news.

0:28:12 > 0:28:18In the sub itself, the precious air was becoming fouler by the minute.

0:28:18 > 0:28:21Each time the men breathed out, oxygen was being replaced with

0:28:21 > 0:28:27poisonous carbon dioxide which had to be mopped up with soda lime.

0:28:37 > 0:28:45In desperation, the Navy at last turned to the man they had once ignored...Charles Momsen.

0:28:48 > 0:28:51Still unrelenting in his drive to improve safety,

0:28:51 > 0:28:55he was quietly tucked away in research and development.

0:28:55 > 0:28:59Following his success with the lung, Momsen had dusted off his plans for

0:28:59 > 0:29:03the rescue chamber, which had originally been scorned by the top brass.

0:29:09 > 0:29:15This is a submarine rescue bell based on Momsen's design.

0:29:15 > 0:29:20It's an incredible simple bit of kit, hardly any moving parts at all.

0:29:20 > 0:29:25It was counted on as being something that would rescue 30-plus men.

0:29:25 > 0:29:29And yet it was just completely unproven.

0:29:29 > 0:29:32Just countless gauges and valves in here.

0:29:32 > 0:29:35Some of them are to control buoyancy,

0:29:35 > 0:29:38some are to control winches,

0:29:39 > 0:29:42and I can't believe you'd get two operators in here and up

0:29:42 > 0:29:47to seven rescued men - there's absolutely no room whatsoever.

0:29:50 > 0:29:53The trick to it is sending it down to the bottom

0:29:53 > 0:29:57and accurately locating it over the submarine escape hatch,

0:29:57 > 0:30:01and the key to that is this thing here.

0:30:01 > 0:30:06There's a rubber gasket under there and that provides a perfect seal over the hatch.

0:30:06 > 0:30:09When this reaches the submarine,

0:30:09 > 0:30:13the water is blown out of it and the water pressure itself,

0:30:13 > 0:30:17which at the Squalus' depth was about 120 lbs per square inch,

0:30:17 > 0:30:22pushes this on to the submarine and squeezes it in place.

0:30:22 > 0:30:29It provides a perfect seal, the men can open up the hatch from inside and enter into here.

0:30:30 > 0:30:36The problem, though, is if this isn't sat absolutely level,

0:30:36 > 0:30:43you get an imperfect seal, the whole of the sea can just rush in - complete disaster.

0:30:47 > 0:30:53'Rescue vessels, led by the Falcon, locate the sub and prepare to send down a newly developed rescue bell.'

0:30:53 > 0:30:55It was Momsen's big moment.

0:30:55 > 0:30:59With 33 lives at stake and time running out, the Navy had

0:30:59 > 0:31:03to take a chance with the maverick inventor and his innovative chamber.

0:31:05 > 0:31:10'Never before has a diving bell like that been used for actual rescue.

0:31:10 > 0:31:12'Will it work, and at that depth?

0:31:12 > 0:31:15'Aboard the rescue fleet, they can only hope.'

0:31:15 > 0:31:21For the chamber seal to work it had to fit precisely over the sub's escape hatch.

0:31:24 > 0:31:30This meant a diver had to go down first to attach a guide cable to the hatch handle.

0:31:33 > 0:31:38The divers who took on this challenge were the astronauts of their day.

0:31:38 > 0:31:42Tough and determined, they risked their lives to push the

0:31:42 > 0:31:47boundaries of human knowledge, with only the most primitive equipment.

0:31:47 > 0:31:51And this is the kind of kit they had to use.

0:31:51 > 0:31:56It's called hard-hat gear and it's very heavy and cumbersome.

0:31:56 > 0:32:00One boot alone, this weighs about ten kilos.

0:32:00 > 0:32:05So some real problems with it. Firstly, you can only dive very, very close to the ship

0:32:05 > 0:32:08because the diver is lowered down from the boat on the surface.

0:32:08 > 0:32:14Secondly, they're pulling a long air hose behind them and that air hose in Momsen's case

0:32:14 > 0:32:19would have been 75 metres long so it would have weighed a ton, making the dive almost impossible.

0:32:21 > 0:32:24But it wasn't just the diving gear that was primitive.

0:32:24 > 0:32:32At the time, we only had a very basic understanding of how our bodies react to being at pressure.

0:32:32 > 0:32:36So Momsen dedicated himself to learning how that happened

0:32:36 > 0:32:42and he developed diving tanks, just like this one used by the Royal Navy here at Gosport.

0:32:52 > 0:32:57What Momsen and his team were beginning to discover was that as a diver descends, water pressure

0:32:57 > 0:33:03squeezes nitrogen from the air being breathed into a diver's bloodstream and body tissues.

0:33:15 > 0:33:19At high pressure, like there are right here,

0:33:20 > 0:33:27at 30 metres, at high pressure, this nitrogen affects our thinking.

0:33:27 > 0:33:30It's a very pleasant feeling, let me tell you,

0:33:30 > 0:33:38but it can lead to problems because it feels like a mildly drunken state

0:33:38 > 0:33:43and it means that, as pleasant as it feels to me, and I've had it,

0:33:43 > 0:33:47and I guess I must be experiencing it right now,

0:33:47 > 0:33:51it means that on a deep work dive, it could lead to fatal mistakes.

0:34:04 > 0:34:0924 hours after the Squalus went down, the first diver was ready

0:34:09 > 0:34:13to be lowered into the freezing waters of the North Atlantic.

0:34:13 > 0:34:19'Deep in the sea there, 33 men are alive, in danger of dying for lack of air.

0:34:19 > 0:34:23'"Get the living out!" is the cry as down goes the diver.'

0:34:25 > 0:34:27The diver was Martin Sibitzky.

0:34:36 > 0:34:40His task was crucial to the rescue - he had to fasten the cable which

0:34:40 > 0:34:44would guide the bell down to the sub's escape hatch.

0:35:01 > 0:35:05With the concentration of carbon dioxide rising with every breath,

0:35:05 > 0:35:09the air in the sub was becoming more poisonous by the minute.

0:35:18 > 0:35:21Sibitzky had to succeed, and quickly.

0:35:21 > 0:35:25On this mission there was no room for error.

0:36:04 > 0:36:08When Sibitzky got down there and started to work really hard

0:36:08 > 0:36:10dragging that heavy cable around,

0:36:10 > 0:36:16he was breathing more air, which meant that he got nitrogen narcosis.

0:36:16 > 0:36:21He became physically fatigued and very confused, almost drunk.

0:36:24 > 0:36:30The rescue was on the verge of collapse when, back on deck, Momsen stepped in.

0:36:34 > 0:36:42Momsen knew exactly what Sibitzky was going through, so he talked him through it, step by careful step.

0:36:45 > 0:36:53Momsen helped Sibitzky gather his thoughts and overcome the effects of nitrogen narcosis.

0:36:53 > 0:36:57At last he was able to clip the cable on.

0:37:04 > 0:37:07The first stage of the operation was complete,

0:37:09 > 0:37:12but the hardest part was still to come.

0:37:12 > 0:37:17Now it was time for Momsen's chamber to be put to the test.

0:37:17 > 0:37:20'The crew of the rescue chamber climb in for their risky adventure.

0:37:20 > 0:37:24'The idea is to lower it onto the sunken sub, make it fast to a hatch,

0:37:24 > 0:37:28'open the hatch and bring the survivors up into the rescue chamber.

0:37:28 > 0:37:32'So beneath the surface it sinks, for life saving without precedent.

0:37:32 > 0:37:34'This occurs a little more than 24 hours

0:37:34 > 0:37:39'after the US Submarine Squalus sank while making a practice dive off Portsmouth.'

0:37:41 > 0:37:45Lowered by a support cable, the chamber began its descent.

0:37:48 > 0:37:52Though it had never been tested in a real rescue situation,

0:37:52 > 0:37:55it was the only hope for the men in the Squalus.

0:38:02 > 0:38:05But would it work? Would the seal hold?

0:38:15 > 0:38:20At 12 noon, the chamber landed over the escape hatch.

0:38:41 > 0:38:44The seal held.

0:38:49 > 0:38:50Yeah!

0:38:53 > 0:38:5930 hours after the Squalus first hit the bottom, the unbelievable had happened.

0:38:59 > 0:39:02A rescue mission had reached the submarine.

0:39:06 > 0:39:10Carl Bryson watched the first eight men get into the bell.

0:39:10 > 0:39:15They were the crew members most affected by the cold and poor air.

0:39:20 > 0:39:24It was essential to get the weakest to the surface first.

0:39:24 > 0:39:28No-one knew how long the rescue would last, if the weather would hold

0:39:28 > 0:39:35or indeed if the bell could actually manage the four journeys needed to lift the survivors to safety.

0:39:41 > 0:39:46Under Momsen's orders, the bell was raised carrying the first survivors.

0:39:49 > 0:39:53Valves let in air to the ballast tanks,

0:39:53 > 0:39:57and inch by inch, the chamber rose...

0:39:57 > 0:40:00..guided by the cable to the ship above.

0:40:08 > 0:40:12For now, everything seemed to be working perfectly.

0:40:18 > 0:40:22At last, the bell made it to the surface.

0:40:28 > 0:40:30'There is it bubbling and breaking the water,

0:40:30 > 0:40:34'the dramatic sight, the sudden appearance of the diving bell.

0:40:34 > 0:40:38'All the rescue power of the Navy mobilised and here is the climax,

0:40:38 > 0:40:41'the rescue chamber coming up from its first descent.

0:40:45 > 0:40:47'Hoisted up. What's in it?

0:40:47 > 0:40:50'There are anxious wives and family waiting tensely.

0:40:50 > 0:40:56'Open it up and then out they climb, survivors, the first one.

0:40:56 > 0:41:01'So weak he has to be helped after being entombed for 24 hours at the bottom of the sea.

0:41:01 > 0:41:08'One after the other, seven in all are brought up in this first trip of the rescue chamber.'

0:41:08 > 0:41:10It was a historic moment.

0:41:10 > 0:41:14For the first time ever, men had been rescued from a submarine on the sea floor

0:41:14 > 0:41:20'and in that instant everything Momsen had worked for was validated.

0:41:20 > 0:41:24But it was far from over. There were still 25 men to be brought up.

0:41:24 > 0:41:29The sub was freezing and the air was getting fouler by the minute.

0:41:29 > 0:41:31There was no time to waste.

0:41:33 > 0:41:40The next two dives went without a hitch, with 18 more men being brought up safely to the surface.

0:41:42 > 0:41:49The chamber was sent back down to the Squalus for the final time, a little before 8pm.

0:41:49 > 0:41:54For Carl Bryson and the last few survivors, struggling against rising carbon dioxide

0:41:54 > 0:42:01and the constant threat of chlorine gas, it seemed to be the end of their ordeal.

0:42:01 > 0:42:05So we were all up there and...waiting.

0:42:07 > 0:42:09Seemed like it took hours.

0:42:09 > 0:42:13Man, it was cold and the air was horrible.

0:42:13 > 0:42:15It was getting worse all the time.

0:42:25 > 0:42:28How did it feel getting in that bell?

0:42:28 > 0:42:33Well, it felt good to get in the bell, but when it jammed, it didn't feel so good.

0:42:43 > 0:42:47The bell had only risen about ten metres when it stuck fast.

0:42:50 > 0:42:55The main cable running down from the bell to the sub below had jammed.

0:43:04 > 0:43:10Diver Walter Squire was sent down into the water to free the stuck cable.

0:43:10 > 0:43:12He made his way down tentatively.

0:43:24 > 0:43:27Squire fumbled around for the cable a few metres below the bell,

0:43:27 > 0:43:30he tried to free it but it wouldn't budge.

0:43:30 > 0:43:34So on Momsen's orders, he cut it.

0:43:38 > 0:43:41Now the full weight of the nine-and-a-half-tonne chamber was

0:43:41 > 0:43:47hanging from a single support cable running to the ship above.

0:43:51 > 0:43:53Just when it seemed the worst was over,

0:43:53 > 0:43:57the diver returning to the surface noticed something disastrous.

0:43:57 > 0:44:02The cable left holding the chamber had begun to unravel and snap

0:44:02 > 0:44:07and the bell was now dangling from a last single strand.

0:44:07 > 0:44:12The men's lives were literally hanging by a thread.

0:44:12 > 0:44:17Afraid that this last strand would break, Momsen had to order the chamber gently lowered back down to

0:44:17 > 0:44:23the sea bed, so just moments from triumph, the rescue had stalled.

0:44:37 > 0:44:42Momsen had them drop us back down in the mud, we were up to 150 foot level then.

0:44:50 > 0:44:55They dropped us back down because if that cable had parted

0:44:55 > 0:45:01and the exhaust cable and the air cable, then we would be lost.

0:45:05 > 0:45:11With the last of the survivors trapped inside the bell, Momsen came up with an all-or-nothing plan.

0:45:11 > 0:45:14It was highly risky, but it was their only hope.

0:45:16 > 0:45:20He reckoned if the operators inside the bell could carefully open the

0:45:20 > 0:45:25valves and blow more compressed air in, they could control its buoyancy,

0:45:25 > 0:45:30and his gamble was that they could make it weightless - neither rising nor sinking.

0:45:30 > 0:45:37If it worked, it would be light enough that it could be carefully hauled up, hand over hand.

0:45:37 > 0:45:42If it didn't, the cable would break and the men would be lost.

0:45:50 > 0:45:56He told McDonald to blow for ten seconds, you know.

0:45:56 > 0:45:59So McDonald blow the lower compartment.

0:46:06 > 0:46:08Then blow 20 seconds...

0:46:11 > 0:46:14Then he blow 10 seconds.

0:46:24 > 0:46:28Finally, they pulled us clear of the mud

0:46:28 > 0:46:33and they had all these people up on the deck,

0:46:33 > 0:46:39pulling this thing by hand and we got up to about 150 feet and

0:46:39 > 0:46:41we went right to the surface like that.

0:46:41 > 0:46:45'One of the greatest rescues in the annals of the sea, men saved

0:46:45 > 0:46:49'from the sunken submarine Squalus off Portsmouth, New Hampshire.

0:46:49 > 0:46:51'Every one of the living brought out alive.

0:46:51 > 0:46:56'In the history of the sea, a sunken submarine represents the depth of terror and horror.

0:46:56 > 0:46:59'This rescue represents a height of glory.'

0:47:01 > 0:47:03We got to the surface...

0:47:05 > 0:47:09and I was frozen, man, oh, man.

0:47:12 > 0:47:14I tell you, we were lucky, really lucky.

0:47:17 > 0:47:22And we had the right people in the right place at the right time.

0:47:26 > 0:47:27That makes the difference.

0:47:34 > 0:47:39Momsen had done it, he'd saved the lives of 33 men.

0:47:39 > 0:47:43The rescue of the crew from the Squalus showed for the first time

0:47:43 > 0:47:48that something really could be done for men trapped on the ocean floor.

0:47:49 > 0:47:54It was a pivotal moment in the history of undersea exploration.

0:47:54 > 0:48:00The Squalus rescue, carried out under the glare of the world's press, had put submarine

0:48:00 > 0:48:07safety firmly on the agenda, and within six months of the Squalus sinking, the US Navy

0:48:07 > 0:48:11had offered the diving bell plans to 13 other countries

0:48:11 > 0:48:15in a bid to make submarines safer round the world.

0:48:19 > 0:48:22As a proven success, it was adopted by other navies.

0:48:27 > 0:48:32And even today, a version of the rescue chamber is still in use.

0:48:35 > 0:48:37It's called the McCann chamber.

0:48:37 > 0:48:40Named after Momsen's successor in the development programme.

0:48:48 > 0:48:51Thanks, mate. I'm here, courtesy of the Italian Navy,

0:48:51 > 0:48:56to take part in a submarine rescue training exercise and I'm going to go down here in a McCann bell, which

0:48:56 > 0:49:00is essentially the same piece of kit that was used in the Squalus rescue,

0:49:00 > 0:49:02to go down to a submarine at 40 metres,

0:49:02 > 0:49:07to see what it was really like for those rescuers and for those men from the Squalus.

0:49:07 > 0:49:09Thanks very much.

0:49:09 > 0:49:11Thank you.

0:49:27 > 0:49:29Very good.

0:49:38 > 0:49:42HE SPEAKS ITALIAN

0:49:42 > 0:49:44I can feel the pressure

0:49:44 > 0:49:46increasing now.

0:49:46 > 0:49:48That's because the water is coming

0:49:48 > 0:49:53in the lower part of the bell and squeezing all the air into this part of the chamber.

0:49:53 > 0:49:55Yeah.

0:49:58 > 0:50:01The bell is noisy, it looks primitive,

0:50:01 > 0:50:05the air pressure varies wildly as you go up and down, but it works.

0:50:05 > 0:50:08The Italians see it almost as an elevator that can run

0:50:08 > 0:50:11back and forth from the surface to the sea bed.

0:50:18 > 0:50:20We've just landed on a submarine!

0:50:27 > 0:50:34It's fantastic to think that a design which is essentially from the '30s is still used today.

0:50:34 > 0:50:37And it's not just the Italians.

0:50:37 > 0:50:42The Turks, Indians and the US still use essentially the same design

0:50:42 > 0:50:48as Momsen's original bell that triumphed in the Squalus rescue.

0:50:48 > 0:50:51It's really surreal, actually, because there's the submarine,

0:50:51 > 0:50:54that's the top of the submarine,

0:50:54 > 0:50:56we're 40 metres in the bottom of the sea.

0:51:07 > 0:51:11It's just amazing... going down to a submarine

0:51:11 > 0:51:12whilst on the bottom of the sea.

0:51:18 > 0:51:22Oh, wow.

0:51:22 > 0:51:24Hey, thanks for this, guys.

0:51:24 > 0:51:26Thanks very much.

0:51:28 > 0:51:33Good Italian espresso served at 40 metres on the bottom of the Med.

0:51:33 > 0:51:38I'm going to remember this next time I'm scuba diving at 40 metres and freezing.

0:51:38 > 0:51:42Dry, good coffee, good company...

0:51:42 > 0:51:44Here we go.

0:51:49 > 0:51:54The Squalus rescue was a turning point in the development of underwater technology.

0:51:56 > 0:52:03New devices were pioneered that led to some remarkable equipment like this one-atmosphere diving suit.

0:52:06 > 0:52:11In one of these, a diver can work hundreds of metres down on the ocean floor, allowing the construction

0:52:11 > 0:52:16and maintenance of many of today's most ambitious engineering projects,

0:52:16 > 0:52:21like North Sea oil platforms and the undersea pipelines leading from them

0:52:21 > 0:52:24which run hundreds of miles along the ocean floor.

0:52:24 > 0:52:29These developments would have seemed impossible before Momsen's triumph.

0:52:31 > 0:52:37After the Squalus rescue, Momsen was promoted to Commander and his prestige in the Navy just rocketed.

0:52:37 > 0:52:40He used his influence to launch a whole new era

0:52:40 > 0:52:44of underwater technology and he became the father of modern diving.

0:52:44 > 0:52:51One of his most significant contributions was the development of new mixed gasses for deep diving.

0:52:51 > 0:52:58By replacing the nitrogen in the air with helium, he completely eliminated nitrogen narcosis.

0:52:58 > 0:53:02That meant that professional divers like myself can dive deeper, we can

0:53:02 > 0:53:07have shorter decompression times and underwater work is just safer.

0:53:09 > 0:53:15In the '60s, Momsen's son, also called Charles, was a real chip off the old block.

0:53:15 > 0:53:19He carried on the family tradition by developing the mini-sub Alvin,

0:53:19 > 0:53:26seen here looking for a hydrogen bomb lost at sea after a mid-air collision involving a B52 bomber.

0:53:30 > 0:53:34Since Alvin was first designed, mini-subs have become lighter

0:53:34 > 0:53:39and more manoeuvrable, with ever more specialised functions.

0:53:39 > 0:53:45Nowadays they're used all over the world, both by navies and civilian contractors.

0:53:49 > 0:53:55As well as submarine rescue and training, they're used for things like investigating wrecks, searching

0:53:55 > 0:54:02for lost aircraft, inspecting marine structures and even filming the secret habits of deep-sea creatures.

0:54:05 > 0:54:12And one man's vision of what was possible beneath the sea helped pave the way for technology like this.

0:54:14 > 0:54:17Momsen was a true pioneer.

0:54:17 > 0:54:24He revealed to the world that hugely complex diving operations can take place deep below the surface.

0:54:24 > 0:54:31The rescue of the Squalus gave people confidence as they dived ever deeper into this alien world.

0:54:34 > 0:54:36Momsen gave hope.

0:54:36 > 0:54:42So should things go wrong down here in the abyss, we know that help can be on its way.

0:54:45 > 0:54:53After a lifetime dedicated to the safety of men at sea, Momsen died in 1967.

0:54:54 > 0:55:00In 2004, the Navy paid him its highest honour and named a destroyer after him.

0:55:05 > 0:55:10As for the Squalus itself, it was salvaged from the deep in the months after it sank.

0:55:14 > 0:55:19Recommissioned as the Sailfish, it fought through the Second World War.

0:55:23 > 0:55:27Her conning tower is still preserved at Portsmouth Navy Yard

0:55:27 > 0:55:30as a lasting tribute to the men who served on her.

0:55:34 > 0:55:37How does it feel to be on here now, Carl?

0:55:37 > 0:55:40Well, brings back a lot of memories.

0:55:40 > 0:55:44I lost some very close friends on this boat.

0:55:53 > 0:55:54It...

0:55:56 > 0:56:00It was a sad thing, it was a heavy price to pay.

0:56:02 > 0:56:06Do you think it gave you a unique perspective on life itself?

0:56:06 > 0:56:09Oh, yes, oh, yes. Well...

0:56:09 > 0:56:11let's say I was always lucky.

0:56:11 > 0:56:13I was lucky since then.

0:56:13 > 0:56:17I was very lucky, I married a wonderful woman and I got

0:56:17 > 0:56:22three wonderful children and six wonderful grandchildren.

0:56:22 > 0:56:25Can't get much luckier than that!

0:56:25 > 0:56:28If Swede Momsen was here today, what would you say to him?

0:56:28 > 0:56:30Thank you, Swede.

0:56:31 > 0:56:33You betcha.

0:56:34 > 0:56:40I...I couldn't emphasise my gratitude enough, believe me.

0:56:40 > 0:56:45I have a medication that I take in my room

0:56:45 > 0:56:50and I have a picture of Swede about so big up on my bookcase

0:56:50 > 0:56:55and when I take the medication I always say, "Thank you, God,"

0:56:55 > 0:56:58and "Thank you Swede."

0:57:20 > 0:57:22Subtitles by Red Bee Media Ltd

0:57:22 > 0:57:24E-mail subtitling@bbc.co.uk