One sunny morning last November, Ben Hooper, a 38-year-old former policeman, waded into the Atlantic Ocean from a beach in Dakar, Senegal, and plunged right in. In film of the moment, Hooper appears thick set, almost podgy. He’d spent the past year bulking up, and now layers of fat concealed muscle beneath. He wore a sports watch, black goggles provided by a sponsor, and a pair of tight blue shorts. The sun had risen early, and by 10.33am, when Hooper entered the water, the ocean temperature had reached 30C – a lukewarm bath. A group of reporters gawked from the shallows. Most of them squinted in the bright light.

Hooper had been in Dakar for six weeks, preparing to swim to Natal, northeast Brazil, 1,879 miles away. If successful, he would become the first person to swim across the Atlantic Ocean – 12 miles a day for over 140 days straight – an unfathomable feat. As he swam away from the beach, Hooper began to feel tears in his eyes. A mile later he “cried like a baby”. The launch represented the culmination of three years’ planning, and the relief was overwhelming. Later that day, as the adrenaline wore off and the magnitude of the task began to sink in, he swam against currents that made it difficult to achieve significant mileage. Later, while he recovered on the support boat, a 37-year-old catamaran, he wrote the first in a series of blog posts he’d publish during the attempt. “Spent the night drifting under sea anchor,” it read, “4.5 miles closer to making history.”

A fierce wind drove across the water and at times the swell rose so high Hooper lost sight of his boat

Hooper’s posts were being uploaded to Facebook, and very quickly became difficult to read. On day two, Hooper’s crew lost contact with a second support boat, whose captain had returned to Dakar, refusing to continue with the expedition. A couple of days later, Hooper again faced unusually strong currents, limiting his mileage. Soon, clouds stretched across the vast horizon, sometimes bringing rain, and the ocean became dark and choppy. Hooper began to spend more and more time on the boat, waiting for moments of calm. By day seven he was down on his targets. Fatigue mounted. Low moments became commonplace. “Think of swimming in a washing machine on a heavily soiled cycle,” he wrote of ocean conditions in one post. “I am being thrown around all over the place.”

On Facebook, in part to sustain crew morale, Hooper appeared bright and positive, especially after sessions in which he was able to chalk up substantial distance. But his body was under attack. Small jellyfish stings were regular and sapped energy. While swimming through seaweed, lice nipped at his torso. When the ocean was choppy, waves battered his back, arms and legs, pushing him under, exacerbating exhaustion. In poor conditions, Hooper was in danger of injuring himself getting on and off the boat, and every now and then he would take a hit from a kayak that glided alongside him for support. During the morning session of day 17, he was sick, twice. On day 18, he began to complain of neuralgia.

Hooper had chosen a November launch date for favourable conditions, but the weather turned against him. Now a fierce wind drove across the water, and at times the swell rose so high that Hooper lost sight of his boat.

On day 21, Hooper swam blindly into the half-eaten remains of a Portuguese-man-of-war, a jellyfish whose venom paralyses its victims. Hooper began to writhe in pain, unaware of the cause. When he was retrieved from the water, the crew discovered stings up and down the right side of his body. A section of tentacle was still attached to his shoulder and had to be removed. Every now and then his eyes would roll into the back of his head and, as his speech began to slur and his blood pressure plummeted, he struggled to remain conscious. Hooper later told me that, at one point, he was “on my way out”, and that the ship’s medic, Pamela Mackie, “brought me back” to life. For hours, Hooper remained in significant danger. Pain coursed through his body like an electric current. For support, Mackie reached a British trauma surgeon by satellite, who told her that renal failure was an acute possibility. If his kidney packed up, Hooper would not survive.

Beach boy: Hooper in Dakar, plump and strong, in the moments before he set off. He was hoping to cover up to 12 miles a day for at least 20 weeks. Photograph: Seyllou/AFP/Getty Images

Hooper spent the next four days on the boat, recuperating. On day 26, he re-entered the water and swam two miles, still sore from the attack. Three days later, in stormy seas, a steering cable snapped and required repair. The storm built. Waves rose to 30ft, crashing around the crew like ironic applause. Now clouds covered the sky and everything appeared eerie. The rain poured. The wind grew in speed and force. The catamaran, perhaps betraying its age, creaked and groaned.

Finally, on 15 December, Hooper put out a press release, announcing the expedition’s end. Overnight, a storm had reared up, and damage to the boat had been deemed “severe enough to warrant a reappraisal” of the attempt. Further damage, the boat’s captain, Nigel Taylor-Schofield told me, would have “compromised my ability to get him out of the water”, which might have been fatal. Whereas Hooper’s blog posts could be playful, here his tone was defiant. “We have NOT failed,” he wrote. “We have achieved and gained the knowledge to succeed in the future.” Later, in a separate message, Hooper added: “I have never doubted my ability to swim across an ocean. My family have never doubted me. I believe this incredible challenge to be possible.” He’d spent 33 days at sea. Of the expedition’s scheduled 1,879 miles, he had swum 86 – 4.5% of the journey – and lost 2st. He signed off, curiously upbeat: “Christmas is coming, I’m no longer fat. I’m on my way to Natal with my Santa hat.”

One day in May, I met Hooper in Cirencester, near his Gloucestershire home. We sat on a park bench discussing the details of his attempt – what went well, what didn’t. Hooper had returned to the UK in March and now he appeared deep in a state of reflection. One question bugged him: should he plan a new attempt?

I wanted to push myself, to see how far I could go. Because a lot of things I’ve tried in life haven’t worked out

Hooper made the decision to swim the Atlantic in the winter of 2013. For a year he developed the foundations of an expedition, often spending “hours and hours and hours” alone online, searching for relevant information. He worked out that strong east-to-west trade winds would create favourable crossing conditions over the winter period, and that the water at that time of year would be warm and inviting. He also saw that Dakar to Natal would represent the shortest crossing, but that the route would be shared by migrating sharks. He began to amass a long list of other potential dangers, including hypothermia, hyperthermia, exposure, mass calorie deficit, the great white shark, the oceanic whitecap shark, the Portuguese-man-of-war, and another jellyfish, the Atlantic sea nettle.

Still, Hooper persevered. For three years he didn’t work, concentrating instead on being “a full-time athlete” and running the expedition. (He relied heavily on donations to survive.) By 2015 he felt physically ready. He had swum “12 million metres” in training, he told me, mostly in a local pool but sometimes in ocean conditions in Florida and the Mediterranean. With investor funds he bought a boat. Later he purchased supplies and a communications system. Tentatively, he lined up a crew. In August 2016, the catamaran sailed to Dakar, ready for launch. Hooper followed a month later.

When we met, I asked him why he decided to swim across the Atlantic, and why he might try again. He answered that, in completing such a monumental feat, he could “inspire others”, including his eight-year-old daughter, Georgie, and raise money for charity. But, later in our conversation, a more complicated motivation emerged. In 2006, a car crash that brought to a halt his police career sparked a period of depression, and in 2013, following a series of personal setbacks that would result in an affair and the breakdown of a long-term relationship, the illness returned. Suddenly, his “personal life was a mess”. He was finding it difficult to sleep. Eating became an effort. “I wasn’t happy,” he said. “I felt like I was failing in every angle of my life.”

Surface tension: a Portuguese-man-of-war similar to the one Hooper encountered after three weeks, its poison almost killing him. Photograph: Stephen Frink/Alamy Stock Photo

Recognising the decline, Hooper sought an activity through which he could renew his focus and, recalling an early childhood ambition to swim across an ocean, he landed on the idea of a transatlantic expedition. “Not to say that there was ego at play would be a lie,” he said. “I wanted to push myself, see how far I could go. Am I capable of achieving more and not killing myself? Because a lot of things I’ve tried in life haven’t worked out… I saw it as an opportunity to try and redeem myself.”

Transatlantic swimming has a colourful history. In 1995 a 42-year-old Frenchman, Guy Delage, washed up on a beach in Barbados, claiming to be the first person to have done the crossing. Delage had spent 55 days at sea and covered 2,335 miles. At one point, reported the New York Times, he had given a shark a “sharp kick in the nose” before dashing to the safety of his raft. Later, perhaps feigning modesty, he told a reporter at the French paper Libération that “I did nothing superhuman or extraordinary,” before saying he would never swim again. Three years later, another French-born swimmer, Benoît Lecomte, swam from Hyannis in the US to Quiberon in France, covering 3,716 miles in 73 days. He, too, was tracked by a shark – this time for five days – and he too declared himself the first person to cross the Atlantic.

Both swims were celebrated around the world. But after each attempt, questions began to surface about their credibility. In the aftermath of the Delage swim, experts noted that the raft on to which the Frenchman clung must have been equipped with a kind of sail, thus making it impossible to know exactly how much of the trip was human-powered. Following the Lecomte swim, reporters noted that because he ate and slept onboard a support boat, which drifted with favourable currents overnight, it was equally difficult to work out exactly how much of the distance he had actually swum.

Will he try again? It will be difficult to raise the sponsorship – Hooper estimates he would need about £700,000

When an athlete claims to have accomplished something they haven’t, public reaction can turn nasty. Lecomte mostly escaped criticism. In making the crossing, he raised significant sums for charity. (He is now planning to swim across the Pacific.) But in Delage’s case, reaction turned sour. Before setting out for Barbados from the Cape Verde Islands, the swimmer had signed an exclusivity agreement with a TV channel, guaranteeing an important windfall. Delage, it turned out, was broke. His motivation had not been human achievement, as many people believed, but money, and when the information was revealed by the press he was roundly ridiculed. “You have to understand that when I left I was saddled with debts,” he told reporters. “I had no choice.”

While Hooper was out in the Atlantic, questions about the legitimacy of his attempt began to surface on a popular marathon swimming forum. Prior to Hooper’s swim, the sport had been rocked by a number of controversies, mostly fraudulent claims of completion, and the community had begun to ramp up efforts to lay bare any kind of scam. Hoping to satisfy potential naysayers, Hooper had promised total expedition transparency. But as the attempt wore on, onlookers began to bemoan the lack of hard data being shared with the public. Hooper’s blog posts were mostly trivial and contained few facts; he would post co-ordinates, but only on rare occasions, making it tricky for spectators to discern his whereabouts. The inconsistency of information raised eyebrows.

Before long, forum members began to investigate Hooper’s past, prompting further questions, mostly to do with training. As a rule, ocean swimmers cut their teeth crossing channels, but prior to the Atlantic effort Hooper had never swum a large body of water. Jennifer Figge, who has completed an Atlantic crossing (although she, too, has had her efforts questioned, not least by Hooper), swum “close to 20 different swims” before attempting an ocean crossing, she told me, including the Gibraltar Strait. But Hooper had foregone the challenge. When I asked him why he’d never completed a significant but shorter swim that might help establish integrity, such as crossing the English Channel, he said, “I’ve always steered away from the Channel… It’s cold. I don’t do cold water. And it’s dirty. End of.”

‘I thought I was on my way out’: Hooper is towed back to the support boat after being stung by a deadly Portuguese man-of-war. Photograph: Chief Productions

By the end of the expedition, most onlookers had come to a collective conclusion: the attempt had been recognised as valid – Hooper was not a fraud, as some had suggested – but it was also labelled incredibly naive. Hooper, no matter how well-intentioned, had somehow remained ignorant of the extent of the challenge, and he’d paid the price. In the words of Dan Simonelli, an open-water swimmer who had helped early on in the expedition and had once been signed on to become its official observer: “Ben really didn’t have the experience.”

One evening in June, I had another conversation with Hooper over the phone. I’d called to ask about his plans for a second attempt. In May, when Hooper had mentioned another expedition – “I don’t think I could live with someone else turning up and doing it” – he had been careful not to commit publicly to timings. He still hasn’t made any further announcements. “We’re very much at that very early stage,” he says now. “Just chewing it over.”

Hooper has a list of things he’d require to increase the probability of success. The items are mostly pragmatic: a bigger boat and a more effective communications package, among other things. But a new attempt would also demand a significant number of new sponsors, which are difficult to secure. When I asked Simonelli whether he thought Hooper could manage a second expedition, he said: “I think it would be hard for him logistically to muster the attempt again. That has nothing to do with the swim. But it will be difficult for him to get the sponsorship, the money.” Hooper puts an estimated figure at £700,000, double what he raised for his first expedition.

Partway through our conversation he told me he’d begun to train, but that training was secondary to other things going on in his life. He wanted to spend time with his daughter. He also wanted to secure meaningful employment. He’d previously described his personal financial situation as “dire” – he owes £75,000 to expedition investors alone. Finding regular work is essential, he told me, not just to repay debts, or to plan a second expedition, but to survive.

For the first time he seemed hesitant about a second expedition. “We’ve learned a hell of a lot,” he said. “That’s the thing we can shout about.” But the second attempt doesn’t seem to be his priority. “We’re all trying to work and restabilise our lives,” he said. “I’m obviously trying to dig myself out of a hole.” He paused, then said quietly, “And have a life.”