Underwater horror: Shocking details about the murder of journalist Kim Wall, killed in Danish inventor's homemade submarine

New York Post

25-05-2025

Peter Madsen, a self-taught Danish engineer and inventor, had a favorite pickup line he liked to use on women: 'You want to see my submarine?'
It wasn't a joke. In 2008, when Madsen was 37 , he constructed the UC3 Nautilus, which at the time was the largest amateur submarine in the world. He built it in his private lab, in a shipyard lab off the coast of Copenhagen, Denmark. Though he was married at the time, he would often 'frequent BDSM clubs and private fetish parties,' seeking out what he called 'a web of 'crazy ladies' on the side,' writes Matthew Gavin Frank in his new book, 'Submersed: Wonder, Obsession, and Murder in the World of Amateur Submarines' (Pantheon), out June 3rd.
6 Amateur submarine builder Peter Madsen is serving a life sentence for the murder of Kim Wall.
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His obsession with submarines (and women) ended with deadly consequences. On August 11, 2017, he agreed to take Swedish journalist Kim Wall, who was writing a story about him, on a brief submarine journey in Køge Bay. The 30-year-old woman was brutally assaulted and murdered by Madsen, who was 46 at the time.
Wall's torso washed up on a beach almost two weeks later, and her various other body parts were eventually discovered. Madsen was accused of torturing Wall before killing her, dismembering her body, and having 'sexual relations other than intercourse of a particularly dangerous nature,' according to court records, with stab wounds found in and around Wall's genitals.
It was shocking that Madsen, who had no previous history of violence, could commit such a horrifying crime. But as Frank argues, a passion for submarines 'can ruin a person for the surface,' and sometimes the compulsion to sink to great depths can 'dovetail with darker, more threatening traits.'
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Madsen may have acted alone, but he was part of an 'eccentric micro-community of DIY submersible enthusiasts,' writes Frank. And their fascination with underwater travel might be symptomatic of something more sinister than just Jacques Cousteau fantasies.
Since 2002, the PSUBS (or 'personal submersibles') collective has held an annual convention in Muskegon, Michigan, where hundreds of would-be submarine engineers — mostly white men ranging in age from their 20s to their 70s — gather to discuss their hobby and show off their inventions.
They are self-­described 'misfits' who live off the grid and 'have a distrust of government ranging from healthy to conspiratorial,' writes Frank. The lure of submarines is about more than just mastering the sea. For them, it's an escape. Water is where 'those prescient enough to have the machines to pilot themselves there can retreat and start fresh once we've sufficiently depleted the land,' the author asserts.
Most of the mean are self-taught, avoiding a formal education for a DIY aesthetic.
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'Just like looking up how to fix a leaking faucet, Google can show you how to build a personal sub,' one of the men, Hank Pronk, told the author. The 60-year-old inventor is self-employed as a house mover, but taught himself submarine engineering by watching online videos.
6 The crime — and the subculture behind it — is the subject of a new book.
In 2020, Pronk, who is based in Fairmont Hot Springs, B.C., built the Elementary 3000. It has pressure-tested to reach 3,000 feet below the sea and, as of this writing, is the deepest-­diving homemade submarine in the world.
Shanee Stopnitzky, one of the few female members in the personal submersible community, left her PhD program in marine biology at the University of California, Santa Cruz, in 2018 to devote herself to building 'experimental submarines.' She's built several, including one that she's named 'Fangtooth' that was originally painted yellow, but she recently repainted white because, as Stopnitzky told the author, she 'never wants to hear the Beatles song again.'
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Another submarine, which she's named Noctiluca, was purchased from a 'private person' on Craigslist for $60,000.' She joked with the author that finding a great deal on a submarine on Craigslist involves putting 'wife' in the search parameters, 'because once a wife decides something's gotta go, it's, like, really gotta go, and that's how you get the best deals.'
Albrecht Jotten, a German immigrant who lives in a one-room cabin in the woods of Homer, Alaska, dropped out of society to 'work on my art,' he told the author. His 'art' being home-made submarines.
During his conversation with Frank, Jotten gestured towards his library of books, indicating that one day he will be written about like history's other great thinkers. 'The Navy will contact me,' he insisted. 'They'll have me conduct sweeps, ballistic missile research, radar cross-­sectioning, flying infrared nuclear signature evaluation, build their anechoic chambers. They know I know how to stay invisible.'
6 On August 11, 2017, Madsen agreed to take Swedish journalist Kim Wall, who was writing a story about him, on a brief submarine journey in Køge Bay
He also confessed to Frank that he believes the biggest genius who ever lived was Adolf Hitler. 'Look at everything he was able to do, and all of the people he influenced,' Jotten said.
As for Madsen, his original goal was to become a rocket scientist, but he opted against it because it would mean spending more time in school. '[He] felt that the sea might be a space wherein he could indulge his passions and his desire to be a loner,' writes Frank.
So instead, he pursued an independent education, taking welding courses and apprenticing with various engineers. After raising $200,000 in donations (for what he described as 'the ultimate art project… A political message about individual freedom'), he built Nautilus, a submarine where he felt more comfortable, 'away from the judgmental eyes of the surface dwellers,' writes Frank.
But what caused his brain to snap, and for so many amateur submarine enthusiasts to become so … eccentric?
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6 Wall's torso washed up on a beach almost two weeks later, and her various other body parts were eventually discovered. Madsen was accused of torturing Wall before killing her,
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Dr. Ernest Campbell, a surgeon and diving medicine specialist, told the author that people obsessed with undersea exploration 'have different chemistries and personalities' than the rest of us, mostly because 'of the effects of various gases under pressure.'
Breathing air under increased pressure can mess with the brain in much the same way that alcohol and drugs do, says Dr. David Sawatzky, an expert in diving medicine. Symptoms can include 'laughter, excitement, euphoria, overconfidence, terror, panic, impaired manual dexterity, idea fixation, decreased perception, hallucinations, stupor, and unconsciousness,' says Sawatzky.
It's also a womb fantasy, writes Frank, a need to escape your own self, which is 'similar to the sort of 'regenerative dissociation' that also manifests in those who commit murder.' How might one of them react, Frank wonders, if a woman enters the safe space of their submarine? Would they 'be perceived as threats?' Frank writes. 'Does the fantasy become perforated, reminders of the outside, upper world slipping through the cracks?'
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When Madsen was charged with murder in early 2018, his behavior during the first day of court suggested he wasn't thinking clearly. Meeting with journalists outside the courthouse, he spoke of having 'quite ordinary loving erotic intercourse' with many women on board Nautilus, writes Frank. 'He spoke of enjoying red lipstick, stilettos, and nylon stockings. He waved his arms in the air as he said this, (like) some terrible marionette.'
6 Hank Pronk has built the deepest-­diving homemade submarine in the world.
Hank Pronk/ Facebook
During his own testimony, he brought up the movie Terminator 2 repeatedly and compared himself to the titular character, 'hinting at his latent desire to become part of the machines he built,' Frank writes. 'Madsen expressed that a part of him was Nautilus, and Nautilus was him. They shared a brain and a vision.' When Wall died in his submarine, he said, he 'smacked her cheeks to try to reboot her.'
As for what caused Wall's death, Madsen gave several explanations. At first, he explained that she'd been hit by the 150-pound hatch door, but the medical report showed no signs of head trauma. He also claimed that she'd inhaled poisonous exhaust, but that was also contradicted by coroners.
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He never admitted to killing her, but Madsen did confess to dismembering Wall's body, allegedly while he was in a state of 'suicidal psychosis,' in his words. Although police found Google searches and videos of women being tortured and beheaded on his computer, he denied any knowledge.
Today, Madsen is serving a life sentence at Herstedvester Prison, outside of Copenhagen. He still likes to build things in the prison workshop, but he has far less access since 2020, when he created a wooden 'gun' and used it in an attempted jailbreak.
6 Shanee Stopnitzky is one of the few female members in the personal submersible community.
Shanee Stopnitzky
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'When he was recaptured five minutes later, five hundred meters from the prison, he lifted up his shirt and exposed an explosives belt,' Clark writes. 'If the guards did not let him go, he said, he would detonate it. The belt, too, turned out to be fake, fabricated in the prison's carpentry workshop.'
In prison, as in life, Madsen continues to dream of escape, convinced he could build the perfect tool to make it happen.