Cold Open

It’s just after 9 A.M. on August 29th, 1973, inside Pisces III, a deep-sea submersible 150 miles off the southwest coast of Ireland.

35-year-old Roger Mallinson peers through a tiny porthole as sailors on a launch vessel secure a lifting cable to the outside of the submersible.

Mallinson stretches his aching legs. He and his copilot, 28-year-old Roger Chapman, have spent the last eight hours in this cramped vessel, laying telephone cables on the seabed. Now, they’re back on the surface, waiting for their crewmates to lift them aboard the supply ship. And in a few minutes, they should be enjoying a hot meal and an even hotter shower.

But instead, a shrill alarm sounds. Water has been detected inside the sub. At first, Mallinson isn’t too concerned—condensation often builds up inside the sub and trips the sensors.

But after a few seconds, a panicked voice crackles over the radio. The crew outside has accidentally damaged the hatch of the aft machinery compartment, and water is pouring in.

Before Mallinson can even respond, the sub lurches down violently. The weight of the water flooding into the aft compartment is dragging them down. The depth gauge needle spirals before jolting to a sudden halt at 175 feet.

Mallinson presses his face to the porthole. He can just make out the lifting cable. Pisces III is dangling from it like a pendulum beneath the support ship.

But the strain soon becomes too much for the cable to bear.

And it snaps. With another sickening lurch, the submersible plunges into the darkness, free-falling toward the bottom of the Celtic Sea.

Less than a minute later, Pisces III crashes onto the seafloor. The impact damages the submersible and leaves it stranded on the bottom, trapping pilots Roger Mallinson and Roger Chapman over 1,500 feet beneath the surface. For the next 76 hours, these two men will fight against the deepening cold and the increasingly poisonous air inside their sub, until a dramatic rescue operation lifts them back to the surface on September 1st, 1973.

Introduction

From Noiser and Airship, I’m Lindsay Graham, and this is History Daily.

History is made every day. On this podcast—every day—we tell the true stories of the people and events that shaped our world.

Today is September 1st, 1973: The Deepest Underwater Rescue.

Act One

It’s 10 A.M. on August 29th, 1973, inside Pisces III, only moments after it sank to the bottom of the Celtic Sea.

Roger Mallinson sits motionless in complete darkness, his ears ringing. During their rapid descent, Mallinson switched off the power to prevent the impact with the seabed from starting a fire. But now he can’t see anything.

So for a few seconds, he simply concentrates on breathing. Then, he asks his copilot whether he is hurt. Roger Chapman’s voice emerges from the blackness, saying he’s okay too, and relief washes over Mallinson. They’re both alive, and their submersible seems to be intact.

Mallinson reaches blindly for the main breaker switch. Turning the power back on is risky. If the crash has damaged the battery or the cabling, a single spark could ignite a fire, or even cause an explosion. But they don’t really have a choice. The battery powers the scrubber that removes poisonous carbon dioxide from the air. And the underwater telephone won’t work without it either.

So Mallinson hesitates for a moment, then throws the switch. The lights flicker on, and everything seems all right. But as Mallinson and Chapman’s eyes adjust to the sudden brightness, they see their previously neat and orderly sub is in total disarray. Tools, logbooks, and canisters have been flung from their mounts and now sit in a tumbled mess at the bottom of the metal sphere.

But tidying up can wait, because the pilots suddenly hear a terrifying new sound—the hiss of leaking air. Precious oxygen is draining away. Mallinson knows exactly where the tank is—under his bench seat. He pulls the seat cover aside and reaches a hand into the gap beyond. And feeling along the curved tank, he finds the control valve and twists it shut. The hissing stops.

Trying not to think about how much oxygen they’ve lost, the two men take stock of their other supplies. What they find isn’t encouraging. They have no water on board—just a single can of lemonade, and a damp cheese and chutney sandwich. Mallinson grimaces. He can’t stand cheese and chutney.

Just then, the radio crackles into life. It’s their support ship, the Voyager, urgently requesting that they check in. Mallinson picks up the handset to update Voyager on their situation. They’re cold and thirsty, but at least they’re alive. Even through the static, Mallinson can hear the relief in the operator’s voice as he tells the pilots to hold tight while they come up with a rescue plan. Mallinson finds the familiar voice comforting. They’re fifteen hundred feet underwater, but at least they haven’t been abandoned.

Over the next few minutes, distress calls go out across the North Atlantic. And soon, vessels from the British Royal Navy, the Canadian Coast Guard, and the United States Navy are all heading toward the accident site. But these ships alone won’t be enough. The only way to save the pilots is to send another submersible down to the bottom and attach a line to haul Pisces III back to the surface. But there are few vessels in the world capable of doing that.

Pisces III has four sister submersibles—Pisces I, II, IV, and V. But two of these vessels are thousands of miles away in Canada. One is in port for repairs. And another is operating in the North Sea.

Overnight, though, two of the submersibles are flown to Cork, Ireland. There, the vessels are loaded onto the Voyager, which has rushed back to port to collect them. And as soon as all the equipment is aboard, Voyager heads straight back out to sea.

After battling rough waves for 15 hours, Voyager finally arrives at the location where Pisces III sank. The first rescue submersible is lowered into the water—but the launch vessel that should tug it to a safe distance won’t start. For over an hour, engineers aboard the Voyager battle to get the launch moving without success.

Meanwhile, on the seabed, the situation in Pisces III is worsening. Mallinson and Chapman have switched off the power to protect the battery, and it’s increasingly cold and damp in the sub. They only turn the power back on every hour or so to check in with the rescue team on the surface and to run the carbon dioxide scrubber. But there’s a problem with the scrubber too, and CO2 levels onboard are slowly rising. Both men are becoming drowsy and developing pounding headaches—the first signs that the air is becoming increasingly dangerous to breathe.

Roger Chapman and Roger Mallinson are running out of time. But before their sub can be lifted off the seabed, first, the rescue team will have to figure out exactly where they are.

Act Two

It’s just after 2 A.M. on August 31st, 1973, in the Celtic Sea, more than forty hours after Pisces III sank.

A pilot aboard Pisces II watches through the porthole as sailors from the support ship Voyager unhook ropes from his submersible. The first rescue attempt is about to begin.

Ideally, no one would launch a sub in rough seas in the middle of the night. But precious time has been lost to technical problems. And the two men trapped on the seabed can’t afford for them to wait for daylight.

So black water washes across the porthole as Pisces II sinks under the surface. Strapped to its side is a special rope connected to the support ship above. The plan is for Pisces II to locate the stranded sub, then attach the rope to it. The support ship will then haul in the rope and drag Pisces III off the bottom.

But as Pisces II descends, the natural buoyancy of the rope rips it free of its lashings. By the time the submersible reaches the seabed, it is useless as a rescue vessel.

Still, the sub can complete one important task—it can pinpoint the exact location of Pisces III on the seafloor.

Even though the rescue team knows where the submersible went down, underwater currents could have carried it hundreds of yards in any direction. So Pisces II begins to search.

At this depth, visibility only extends a few feet, so instead of searching by sight, the pilot relies on sonar. The monitor shows him a constantly shifting picture of the underwater terrain. He rotates the sub left and right, while ascending and descending, hoping to spot a sharp, clean echo. But all he sees are the dull, scattered signals created by mud and rock.

But then, suddenly, an object materializes on the edge of his screen. It’s faint and over a mile away, but it’s crisper than anything he’s seen so far and unmistakably manmade. There’s no doubt in the pilot’s mind. He’s found Pisces III.

He radios Voyager with the good news. But while he’s talking, something cold touches the back of his neck. He reaches up with his hands, and his fingers come back wet. He looks up to see beads of water dripping from the ceiling. Pisces II has sprung a leak. He’s going to have to abandon the search before he gets trapped down here as well.

But as soon as Pisces II surfaces, the second submersible is ready to take its place. When Pisces V reaches the seafloor, its pilot aims for the area where his colleague detected the mysterious sonar contact. Descending into the depths, he stares at the monitor, watching for the trapped submersible to show itself. But despite sweeping the area for almost six hours, he can’t find it.

Disappointed, he returns to the surface. But while he was below, the rest of the team has been doing some calculations and has a new search area for the pilot to try. A launch tows Pisces V a mile down current. Then the pilot descends again—and almost as soon as he reaches the bottom, he gets a call over the radio. Aboard the stranded Pisces III, pilot Roger Mallinson can hear the rescue sub’s sonar hitting the hull. It’s a sign that the rescuers are close.

Mallinson decides to stay on the line, saying whether the noises are increasing or decreasing in volume, guiding Pisces V toward his stricken sub. And through this direction, a familiar shape appears on the sonar screen. Until, at last, Pisces III emerges from the gloom.

The rescue pilot eases the manipulator arm forward, trying to thread his lifting line through Pisces III's recovery hook. It's painstaking work, like threading a giant needle while wearing thick gloves. After several attempts, he manages to slip the rope through the hook. But just as he gets ready to secure the line, an eddy pulls at the rope, and it catches on one of Pisces III’s external lights. The rescue pilot gently maneuvers his sub backward to free it. But then the line slips from the manipulator’s grip entirely. The pilot can only watch helplessly as it drifts away in the current.

There’s no way of retrieving it, but Pisces V remains on the seabed for several hours, marking the spot so they don’t lose the stranded sub again. Eventually, a warning light illuminates on the control panel. Pisces V is running out of battery power. So the rescue sub must return to the surface alone.

And as it ascends, there’s a worrying update from the bottom. The carbon dioxide inside Pisces III is building up to dangerous levels. Both men are suffering severe headaches and drifting in and out of consciousness.

Time has almost run out. And if the next rescue attempt fails, the crew of Pisces III will not survive long enough for another.

Act Three

It’s 4:30 A.M. on September 1st, 1973, aboard Pisces III at the bottom of the Celtic Sea, several hours after the latest rescue attempt was called off.

Roger Mallinson wakes to a rough shake on his shoulder. His head is pounding, and his mouth is dry. He opens his eyes a crack and sees his copilot, Roger Chapman, pointing to the porthole. The darkness outside is beginning to fade.

Mallinson stares out the window in confusion. He and Chapman are trapped more than 1,500 feet underwater. There’s no way sunlight can reach them here. Even so, the light grows brighter. And gradually, Mallinson realizes it’s the lights from another sub. Pisces II has come to rescue them.

But they’re far from safe yet. The other pilot still needs to attach the lifting line, and this is where the last rescue attempt failed. Mallinson can’t bear to watch through the porthole. Instead, he leans back on a bench and closes his eyes. He soon slips into unconsciousness.

A few hours later, the crackle of static jolts him awake. It’s the pilot of the rescue sub. With the help of a remotely operated U.S. Navy vessel, two rescue lines are now in place, and they’re about to lift the trapped sub.

As the lines pull taut, the metal hull of Pisces III groans like it’s about to be pulled apart. Then Chapman points to the depth gauge. It’s moving. And the sub is rising.

But the two men feel little relief. Instead, they’re afraid. Going up is almost as terrifying as coming down. Pisces III is buffeted by underwater currents and swings violently on the lifting line, up, down, and side to side. Chapman and Mallinson can only cling on and hope that it might be over soon.

But eventually, the water outside grows lighter—and this time, it is sunlight they can see.

Just after 1 P.M., Pisces III breaches the surface. Divers swarm over the sub and try to release the hatch. But it won’t move. It’s jammed. Chapman and Mallinson remain sealed inside their sub. And their oxygen is almost out. After all the efforts to get them off the seabed, it seems they might now suffocate on the surface.

For nearly thirty minutes, the divers struggle with the hatch until they finally free it.

Fresh air rushes into the sub, tinged with the briny scent of the sea. Mallinson has never smelled anything so good.

84 hours and 30 minutes after they began their dive, Roger Chapman and Roger Mallinson finally emerge from Pisces III, saved by the world’s deepest underwater rescue, a multinational effort that concluded on September 1st, 1973.

Outro

Next on History Daily. September 2nd, 1945. Ho Chi Minh declares Vietnamese independence from France, setting the scene for decades of war.

From Noiser and Airship, this is History Daily, hosted, edited, and executive produced by me, Lindsay Graham.

Audio editing by Muhammad Shahzaib.

Sound design by Mollie Baack.

Music by Thrumm.

This episode is written and researched by Lauren Sudworth.

Edited by Scott Reeves.

Managing producer Emily Burke.

Executive Producers are William Simpson for Airship and Pascal Hughes for Noiser.