Pisces III Submarine Rescued off Ireland’s South-western Coast 1973 | Season 6 – Episode 9
Floats Jan 13, 2026
The rescue of Pisces III, which made world headlines in August 1973, reads like a cliff hanger film script, filled with high drama, mounting tension and a just in time rescue against seemingly impossible odds. At the time, it entered the record books as the deepest underwater rescue ever attempted.
On 29th August 1973, off the south-western coast of Ireland, pilots Roger Chapman and Roger Mallinson were working on the seabed in the Canadian built submersible Pisces III. A routine cable laying dive ended abruptly when a snagged towline caused flooding and sent the submersible plunging to the seabed at a depth of 480 metres (1,575 feet). With only 64 hours of oxygen remaining, the two men shut down all non-essential systems and prepared for a long wait in near darkness. After three days of repeated failures on the surface, a lifting line was finally secured. After 84.5 hours trapped on the seabed, Chapman and Mallinson were brought back to the surface with just 12 minutes of oxygen remaining.
DIVE NO. 325
Pilot Roger Chapman and senior pilot Roger Mallinson began what was intended to be a routine dive, number 325, in Pisces III. The submersible was operating on charter for the British Post Office, laying transatlantic telephone cable approximately 150 miles south west of Cork. Pisces III measured 20 feet long by 7 feet wide and 11 feet high. She had been built by International Hydrodynamics of North Vancouver, British Columbia and launched in 1969.
“It took about 40 minutes to sink down to not far off 500m (1,600ft) and a bit faster to get back up,” Chapman recalled. “We’d do eight hour shifts, going along the surface of the seabed at half a mile an hour, setting up pumps and jets which liquefied the mud, laying cable and making sure it was all covered. It was very slow, murky work.”
Mallinson described the physical and mental strain of working in near zero visibility. “It was like driving down the motorway in thick fog and trying to follow a white line. You had to concentrate beyond belief. One pilot would have the controls in one hand and the manipulator in the other, then we’d swap. It was also uncomfortable. We had to kneel, with our heads by our knees.”
The dive followed an exhausting period for Mallinson, who had been awake for 26 hours repairing a damaged manipulator arm. “I knew Pisces III inside out, having rebuilt it when it arrived from Canada as a wreck,” he said. The submersible had already sunk once before, during sea trials in Vancouver Bay in 1971. One seemingly minor decision would later prove critical. Before the dive Mallinson chose to replace a partially used oxygen bottle with a full one. “I could have got into trouble for changing a half used bottle, but as it happens, if I hadn’t, we wouldn’t have lived.”
THE ACCIDENT
As Pisces III waited to be recovered to the surface, the towline became snagged. The submersible had originally been fitted with tail fins, but these were removed after its purchase by Vickers Oceanics to improve access and handling. Had the fins remained in place, they would likely have prevented the towline from becoming entangled on the machinery sphere.
“We were waiting for the towline to be attached to lift us back to the mother ship. There was lots of banging of ropes and shackles, then suddenly we were hurtled backwards and sank rapidly,” Chapman said. “We were dangling upside down, then heaved up like a big dipper.” The aft machinery sphere flooded, instantly making the submersible more than a tonne heavier. “As we sank my biggest worry was whether we were anywhere near the continental shelf, because if we hit it we’d be crushed.”
Mallinson vividly recalled the descent. “It was very frightening, like a Stuka dive bomber with screaming motors and the pressure gauges spinning around.” All electrical systems were shut down and a 400 lb lead ballast weight was dropped to reduce the rate of descent. In pitch darkness, the two men braced themselves. “We turned the depth gauge off at 500ft as it could have burst. We curled ourselves up and put white cloth in our mouths so we didn’t bite our tongues off,” Mallinson said. At 09:30, Pisces III struck the seabed at a depth of 480 metres (1,575 feet). The impact speed was later estimated at around 64 km/h (40 mph). “We weren’t injured but there was kit everywhere,” Chapman recalled. “Unbeknown to us, we’d hit a gully, so we half disappeared below the seabed.”
ORGANISING THE RESCUE
Telephone contact was established with the surface, and Chapman and Mallinson reported that they were uninjured, their morale was good and they were beginning to organise themselves for a prolonged wait. Despite this fragile lifeline, the precise location of Pisces III remained unknown. As the submersible sank, its surface buoy was lost, making the task of finding her the first and most critical challenge of the rescue. According to Stephen McGinty, author of The Dive: The Untold Story of the World’s Deepest Submarine Rescue, Chapman even sang inside the cabin in the hope that sonar operators might detect the sound. Against the odds, his voice was heard and the rescuers had a location.
Calculations suggested that their remaining oxygen would last until early Saturday morning. Inside the submersible, the two men stabilised the cabin and reduced all activity to conserve oxygen. “If you switch off, you use one quarter of the oxygen. You don’t talk or move,” Chapman said. The internal diameter of the crew sphere was just six feet, and the pilots positioned themselves as high as possible to avoid carbon dioxide pooling at the bottom.
“We hardly spoke, just grabbing each other’s hand to show we were alright. It was very cold, we were wet through,” Mallinson said. “Our job was to stay alive.” On the surface, a major international rescue operation swung into action. The support ship Vickers Venturer was recalled from the North Sea. HMS Hecate was dispatched with specialised lifting gear. An RAF Nimrod aircraft searched overhead. The US Navy remotely operated vehicle CURV III was flown in from California, while the Canadian Coast Guard ship John Cabot sailed to the scene.
PISCES II AND PISCES V
The mother ship Vickers Voyager arrived at Tivoli Docks, Cork at 08:00 to load submersibles Pisces II and Pisces V, which had arrived overnight by air. The vessel sailed again at 10:30. Below, conditions inside Pisces III continued to deteriorate. The pilots had a single cheese and chutney sandwich and one can of lemonade, which they avoided consuming. Carbon dioxide levels were allowed to rise slightly to conserve oxygen.
“We also started thinking about our families,” Chapman said. “I’d just got married. Roger had four young kids and that began to weigh on him.” One unexpected message lifted their spirits. “We got a message from Queen Elizabeth wishing us a quick recovery. We thought it was the Queen herself,” Mallinson said. “Later we learned it was the liner Queen Elizabeth II, which had diverted to stand by. Then came the message, ‘sorry boys, wrong lady’.”
DELAYED RESCUE
“Friday was a disaster from a surface point of view,” Chapman recalled. Pisces II attempted to attach a lifting line, but the rope tore free. Pisces V reached the seabed but initially failed to locate Pisces III, then ran low on power. CURV III suffered an electrical fault and could not be launched immediately.
“By midnight we were almost resigned to thinking it wasn’t going to happen,” Chapman said. Oxygen was exhausted, lithium hydroxide was nearly gone, and conditions inside the submersible were foul and bitterly cold. Mallinson later recalled finding comfort in an unlikely source. “I could hear dolphins on the underwater telephone for the entire three days. That gave me a lot of pleasure.”
At 04:02, Pisces II returned with a redesigned toggle and successfully secured a line to the aft sphere. “Just after 5am it had a line on us. They knew we were still alive,” Chapman said. At 09:40, CURV III descended and attached a second line. Only then did the pilots eat the sandwich and drink the lemonade.
Mallinson remained uneasy. “The aft sphere wasn’t the strong point. I thought it was the wrong decision. At that point, if they’d asked us whether we wanted to be lifted or left alone, we’d have said ‘leave us alone’. The recovery was terrifying.”
LIFT & MIRACLE RESCUE
The ascent began at 10:50 and was immediately violent and disorientating. The lift was halted twice, once at 350 feet to disentangle CURV III and again at 100 feet so divers could attach heavier lift lines. “We were thrashing and rocking about,” Mallinson said. “They needed more ropes so everything could be heaved together.”
At 13:17, Pisces III was dragged clear of the sea. “Apparently they thought we’d died when they looked at us,” Chapman said. “When the hatch opened and fresh air rushed in, it gave us blinding headaches, but we were euphoric.” The hatch took nearly 30 minutes to open. “When it finally went, it went off like a gun,” Mallinson recalled.
The two men had been trapped underwater for 84 hours and 30 minutes. “We started with 72 hours of life support and eked out another 12.5 hours,” Chapman said. “When we checked the cylinder, we had 12 minutes of oxygen left.”
AFTERMATH & LEGACY
Author R. Frank Busby later reflected that “the crew of Pisces III can be thankful they were not 250 miles, rather than 150 miles from Cork.” The rescue demonstrated both the resilience of the Pisces design and the feasibility of deep-sea recovery operations. Pisces III is now preserved and on public display at the Weymouth Sea Life Centre in Dorset.
Chapman later published his account in No Time on Our Side and went on to found Rumic Ltd, which designed the LR5 rescue submersible. Another Rumic vehicle, Scorpio 45, successfully rescued a Russian submersible in 2005. Roger Chapman died in 2020. Roger Mallinson went on to restore steam engines and, in late 1976, became keeper of the steam launch Shamrock, built in 1906, which still steams on Lake Windermere, Cumbria, England today.
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Sources of Information, Photo & Video Credits:
Associated Press (AP)
Grunge Website
IMS Vintage Photos
No Time on Our Side by Roger Chapman
Pastoria
Pisces III submersible: A dramatic underwater rescue – Vanessa Barford – BBC News
Submarine Trapped On Sea Bed – Paddy Smith – RTÉ News
The Shamrock Trust
Wikipedia
Waterline Stories
