If Dirk Zimmerman’s boss fancies a fresh tomato salad, the 35-year-old German hangs up his chef’s apron, dons a headset and takes to the skies. Zimmerman, who has been working on superyachts for more than a decade, has lost count of the number of times he’s been sent out on a ship’s helicopter or seaplane to source food, from courgettes in Oman to truffles in Argentina or vine tomatoes from a nearby Pacific atoll.

“It might shock you to know how much money some people spend privately,” he says as he prepares sushi in the professional-grade kitchen on the 60-metre St David, moored in Monaco. “But to be able to take a helicopter and fly two hours somewhere to get the boss’s preferences makes his day.”

Play Video 7:35 Life and death on billionaires' superyachts – video

As the rich become even richer – 145 more dollar billionaires were minted last year – orders for new superyachts (longer than 24 metres) have hit a record high. More than 500 are being built in shipyards around the world, and with many requiring at least 100 staff, superyachts now employ more than 37,000 people. Britain’s seafaring history has made it the biggest source of employees; crewing on a superyacht is so popular among young adventurers that Southampton Solent University now offers degree-level training at its Warsash Superyacht Academy. Every spring, dozens of young Brits decamp to Antibes on the Côte d’Azur, the unofficial centre for superyacht crew recruitment, where you can wander along the docks looking for opportunities.

While it is a dream job for some, other deckhands and chefs have horror stories of working punishing hours. Accidents, injuries and deaths are also commonplace, with union leaders believing working on superyachts to be more dangerous than life on oil rigs; over the past few years at least three young Brits have died while serving their billionaire bosses. Because many superyachts continually float around the world (this is marketed to some as a way to avoid being registered in any country and hence to avoid paying tax), their crews may not be afforded the same legal protections as those on land. Families complain about a lack of assistance and sympathy from owners and those in charge of the vessel. None of the owners attended the three British men’s funerals.

Michael Hanlon, 22, left Cumbria for his dream job as a deckhand and watersports instructor on 62-metre superyacht Faith, owned by the Canadian fashion billionaire Lawrence Stroll, in March 2013. Less than a month later, and before he’d had a chance to spend any of his first $3,500 (£2,600) monthly pay cheque, he was dead.

Michael, known as Milo to his friends and family, had returned exhausted from a night out to the vessel docked in Antibes on the French Riviera. He had done two shifts back to back, working night and day, then gone to local bars to celebrate sailing across the Atlantic. Faith had been locked up for the night, and Michael climbed to its top in an attempt to get inside via an unofficial emergency entrance. An inquest found he fell from the top deck, hit his head on the quay and drowned. His body was recovered the next day.

Facebook Twitter Pinterest Jacob Nichol, who died last year, aged 24; he fell while cleaning a superyacht. Photograph: SWNS.com

Jacob Nichol, from Cornwall, died last summer, aged 24, two years after he suffered severe brain injuries after falling from superyacht Kibo, while cleaning it as it was docked in a Majorcan port. Jacob, the yacht’s third assistant engineer, had been hanging in a harness when he fell and fractured his skull. His sister, Jenade Moon, said he had never been asked to clean the boat before: his job focused on engine maintenance. The owner of the £90m yacht, Russian billionaire Alexander Mamut – until last month owner of Waterstones, and friend of Chelsea FC owner Roman Abramovich – was not on board at the time.

After 10 days in a coma in a hospital in Palma, Jacob was repatriated to Shropshire, where he needed constant care. In September an inquest recorded a verdict of accidental death. “Our beautiful Jacob has sadly passed away,” his family said. “A young, bright, intelligent, kind soul has left us after an excruciating two years.”

In 2010, Robin Black received a call from the captain of the £15m sailing superyacht Burrasca, on which Black’s son Will was bosun, or officer in charge of crew and equipment. At the time, it was moored at the Monaco yacht show in Port Hercules, the annual beauty parade held in the industry’s global hub. The captain told Black that Will, 28, hadn’t been seen since the night before, when the rib he was piloting (a small boat used to ferry passengers to and from the yacht) collided with another boat. He thought Will may have been knocked overboard.

The captain said: ‘Don’t worry, we threw some flowers over the side and gave his belongings to the police'

By the time Robin, Will’s mother Judith and his sister Rosanna, now 37, arrived in Monaco to join the search, the yacht had left. “The captain said: ‘Don’t worry, we threw some flowers over the side and gave his belongings to the police,’” Rosanna says, fighting back tears as she describes “the worst days of our lives”. “I couldn’t comprehend that the boat had gone before Will was found and before we got there,” she says. “How could they just leave a family to deal with the death of one of their crew, and the police and paperwork and everything? I can’t believe that if something goes wrong – if someone dies – they can just raise the anchor and leave.”

The family don’t know who owns Burrasca, though he is thought to have been a Russian billionaire (owners do not have to declare themselves). He was not on board at the time of the accident. The yacht did not request divers to look for Will’s body, leaving the captain of another superyacht, who was a friend, to pay for search and recovery divers. But they were unable to find Will, who had not been wearing a life vest.

Facebook Twitter Pinterest Will Black, who died aged 28, with his family; his body has not been found. Photograph: courtesy Rosanna Black

Will’s life was not insured. “But it’s not about money,” Rosanna says, “it’s about respect for another life.” She says that the owner didn’t and doesn’t seem to have cared. A spokesman for the yacht’s management did not respond to the Guardian’s requests for comment.

If something goes wrong on a superyacht, it can be incredibly difficult for crew and their families to understand which laws and rights apply. Vessels are often operating in international waters, their day-to-day operations run by management companies on behalf of often unidentifiable owners; their yachts are registered via offshore companies in places such as Panama or the British Virgin Islands.

To add to the confusion, superyachts can be registered with another country and fly their flag, even if the yacht is not based there. At the time of Will’s death, Burrasca was registered in St Vincent and the Grenadines. There was no British inquest, and local authorities recorded this report of the accident: “Mr William Black was on tender duty between the mothership at anchor and the shore. The anchorage was very crowded. Returning to the mothership, the tender hit an unattended vessel that was anchored in the bay. The tender was found drifting with no one on board… Mr Black’s body was not found.”

Will, who had always wanted a life of adventure, had worked his way up from a deckhand on smaller boats to an officer on Burrasca. He’d recently begun his role as bosun on the 55.7-metre yacht and Rosanna says he was passionate about his job. “Will had found his calling. He worked hard, but he played hard, too, and always came back with the most amazing stories,” she says as she shows me photos of Will on a night out with 50 Cent and Jamiroquai. “We still get letters from some of the families he worked for. They send cards for Uncle Whale, as he was called,” she says. “He had a huge personality and everyone loved him.”

Despite the circumstances of his death, Rosanna says she would not discourage others from joining the superyachting world. “I would just tell them to make sure they’re always on top of safety, and to find out who the owner is before they join.”

It’s shorts, T-shirts and deck shoes weather at the Monaco yacht show, as I weave my way through champagne receptions, passing Ferraris and Aston Martins for sale on the quayside. This year’s display of yachts is collectively worth more than £2bn; the combined annual spending on the world’s 6,281 superyachts could wipe out all developing countries’ debts.

There are so many superyachts docked for the show that Top Shop boss Sir Philip Green’s £100m Lionheart has been forced out of its mooring into the Bay of Monaco. The 110-metre Jubilee, which was built for the late emir of Qatar, is on sale for $300m.

On board the six-cabin St David, which is on sale for just under £20m, Zimmerman is preparing canapes for a party. He says the industry keeps many people in well-paid employment, adding that he can’t envisage going back to work on land, as “the pay cannot compare. I have three children, and working here pays for their education.” But, he adds, newbies have to decide early on whether they can sit by and watch their billionaire bosses spend vast amounts enjoying themselves, while appearing not to care about those around them. “It’s a compromise that everyone has to make – can you accept it?”

Liz Brasler, 29, is chief mate, or second-in-command, of one of the yachts in the harbour. She won’t say which but “it’s one of the bigger ones”. She has worked her way up the ranks from deckhand since 2006. “It can be great fun but it’s also exhausting, delivering the highest standards invisibly, magically, with no apparent fuss,” she says. “Owners expect the best in the world. They want to go wherever, whenever, and demand the highest standards without delay. Money is not a problem for them.”

For most of her career, Brasler, who is South African, bunked with colleagues in small cabins; now she has a cabin of her own. But while she has more privacy, she says she can’t remember the last time she had seven hours’ sleep while on charter or at sea.

Has she ever woken up to find an A-list actor on board? “Oh yes, quite often. You can’t get all excited every time you see Tom Cruise. It is a glamorous life. I’ve met some of the most famous people you can imagine. [But] they pay to be invisible – the richest of the rich are sometimes the most discreet.”

The billionaires’ superyacht designer of choice, Andrew Winch, knows all about the needs of the super-rich. We speak on Cloud 9, the 74-metre, £59m yacht he designed for the Australian retail tycoon Brett Blundy; this is the first time he has stepped aboard since he handed it over. Winch, who has designed yachts in a London studio since 1986, created Madame Gu, the 2014 motor yacht of the year, and Phoenix 2, owned by the late Polish billionaire Jan Kulczyk. His yacht designs have proved so popular that he now designs clients’ homes and planes, including Roman Abramovich’s Boeing 767.

“Most clients will have three, four or five houses around the world,” he says. “We have clients we’ve already worked with on their jet and their yacht, and soon there will be a ‘rollover’ and we’ll start on another sequence.”

A wall folds down to create a balcony 'because it’s very nice, when the sun’s setting in Greece, to have a massage'

Of all Winch’s projects, which first take shape at his offices on the banks of the Thames, Cloud 9 was a clear favourite. “He [Blundy] is great fun. This is the second boat we’ve done with him, so we know him very well, and he’s family.”

Everything on board is designed for the owner, from the bedroom suites named after Star Wars characters (his favourite film), to the extra head space above the gym’s treadmill (he’s tall) and the proliferation of chess sets: “He likes to play chess, for several days, with various guests at the same time,” Winch says. In the hair salon, a wall folds down to create a balcony “because it’s very nice, when the sun’s setting in Greece, to have a massage outside”.

A short ride downstairs in the ship’s glass-topped elevator is the “beach club” at the bow. From here Blundy and his guests can hit the water with the boat’s “toys”, including a speedboat for waterskiing, jetskis and what Winch calls a “James Bond-style personal submarine”. A “water sports and boys’ toys” instructor will be on hand to help guests get the hang of it and take care of “all the boring things”, like cleaning and clearing away. For guests who dislike the swell or salt of the ocean, there’s a swimming pool above an espresso bar.

The gym includes a pair of rowing machines and exercise bikes which can be carried up to the bow so the owner and his personal trainer can race each other in the sea breeze. “The captain can be motoring the boat from place to place, and it could feel as if he is pedalling it there,” Winch says. The gym can also be turned into a classroom for Blundy’s two children. Chairs and desks appear from discreet compartments; the walls contain an interactive blackboard and video screen. “They [the children] can join any class anywhere in the world,” Winch says. “They can learn about the history of the ship’s next destination before they get there.”

The ship’s teacher, one of 22 staff, is on hand to guide their learning. There’s also a nanny, personal trainer, masseuse and hairdresser. “You take your life with you,” Winch explains.

“Life on board is perfect for owners – they receive a seven-star service. But for officers and crew it can be a lot more difficult,” says Danny McGowan, the strategic organiser of seafarers’ union, Nautilus International. He has come from their offices in London to the Monaco show to draw attention to the deaths of young workers, highlighting the dangers of working in an industry that to outsiders appears the height of glamour.

“They will often be working very long hours, right around the clock, looking after guests,” says the fair-skinned, red-haired McGowan, sheltering from the sun in Monaco’s famous La Rascasse bar, which a crew recruitment company has hired out for the week. “These are tragic situations where young people have lost their lives, and there are hundreds of other injuries and complaints that aren’t reported.” He says staff have had their passports confiscated and wages withheld; they talk of being sent home for the slightest uniform infraction.

Superyacht owners can view crew as “dispensable and replaceable” and don’t consider the impact on their families. “Often an owner feels they can just get a new third engineer, rather than thinking of the consequences for the individual,” he says. “We’re not here to be up against these billionaires. We want to work with them to make employment in this industry better.”

Most recently, McGowan has been representing the 42-strong crew of a £67m superyacht owned by the Indian multimillionaire Vijay Mallya. The crew, among them several Britons, haven’t been paid for months, and are owed more than $1m. McGowan helped them take their case to court, to have the yacht impounded in Malta. Mallya, a co-owner of the Force India Formula One team, was arrested in London last year over allegations that he supported the team with laundered cash, and Indian authorities are currently seeking his extradition to face trial. He is living in a Hertfordshire mansion while on bail; the yacht, which features a 15-seat cinema and Sir Elton John’s baby grand piano, remains impounded, with some of the crew still on board.

Sitting on the harbour wall overlooking Cloud 9 and a fleet of other superyachts, Fiona Hanlon fights back tears as she remembers the “heartbreakingly impersonal” way she was informed of the death of her 22-year-old son, Michael.

Hanlon has flown to Monaco from the family home in the Lake District to scatter Michael’s ashes. At the same time, knowing he had worked two shifts back to back, she is taking the opportunity to highlight the plight of some other superyacht crew, who she says are often forced to work long hours – conditions that might be illegal in the UK. “It was Michael’s dream job,” she says. He grew up sailing on Windermere. “He had just got his first salary and he’d sent me photographs of the sunglasses and travelling guitar he was going to buy. He was so excited, it was wonderful.”

It was seen as an inconvenience, as the boat was going on to pick up Catherine Zeta-Jones

Michael had been texting his mother daily updates about his adventures sailing across the Atlantic. But on 7 April 2013, Fiona’s phone didn’t ping. She texted him: “Worried about you now – no contact gets me thinking something is wrong – say hello soon please x” followed by, “My baby where are you x x please get in touch angel – we just want to know you are OK.”

The next day his mother was told Michael was missing. “It was seen as an inconvenience, as the boat was going on to pick up Catherine Zeta-Jones,” she says. The following day Michael’s body was found under the yacht by police divers.

The coroner for Cumbria, Philip Sharp, ruled that he died from drowning and recorded a verdict of accidental death. He wrote to the yacht’s registered owner – a PO box in the British Virgin Islands – to raise concerns that “crew members and in this case the deceased were likely to have been asked to work additional shifts when the boat came in to port, potentially causing tiredness”. Sharp’s letter required the yacht’s owner to provide all crew with a key to the boat, and to ensure the captain check the crew are not required to work excessive hours.

An unnamed director of the superyacht’s owner, Pluteus Limited (a company based in Monaco, incorporated in the British Virgin Islands and registered in the Cayman Islands), wrote to the coroner to say: “We are keen to cooperate and address the concerns you have identified as a result of the inquest. However, please note that in doing so, no acknowledgment or admission of failings or liability is intended or to be inferred.”

Facebook Twitter Pinterest Michael Hanlon, who was 22 when he died; he grew up sailing on Windermere. Photograph: courtesy Fiona Hanlon

The director said that access to the yacht had been improved by the provision of keyless codes to all staff. It was also promised that working hours would be monitored, “to ensure crew members are not working additional hours without the requisite rest periods, in particular between shifts, unless the safety of the boat, crew and passengers is in danger”.

“It’s destroyed our family,” Fiona Hanlon says. “Michael wanted to travel the world. Instead he’s in my bag [she carries his urn with her] and I’ve taken him to see the Great Pyramid of Giza, Pearl Harbour and the Great Wall of China.”

Meanwhile, chief mate Liz Brasler is wondering what job she might do next. She says that while working on superyachts has been fun, it can be difficult, demoralising and sometimes dangerous. Friends have been injured and she knows of others who have died. “We’re insured, but it doesn’t cover everything. I know the price of my life,” she says. “And it’s less than my parents think.”

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