Hundreds of thousands of seafarers are facing financial ruin, physical exhaustion and mental health crises as their industry is decimated by coronavirus restrictions.
An estimated 300,000 seafarers around the world – the majority from the Philippines and India - are struggling with crushing debt as they struggle, without pay, to rejoin vessels because of the pandemic.
A further 300,000 are believed to be trapped on board, mentally and physically exhausted, waiting for a crew changeover that never comes.
Shipping industry groups, workers' rights bodies and international institutions like the United Nations have warned of a humanitarian and mental health crisis among key frontline workers, which could ultimately disrupt the supply chains of vital goods around the world or cause an environmental disaster.
Among them is John, a Filipino seafarer who faces financial ruin after being unable to return to his job on a commercial ship since last November.
His Covid-19 test in mid-July came back negative but it was not the end of his ordeal.
"I don't have any other choice but to wait," he told the Telegraph from his hostel in the Philippine capital, Manila.
"Financially, it's very difficult. As seafarers we don't know any other job, and I have to support my parents," he said.
John is torn about his return to work as an able-bodied seaman, doing maintenance work on a cargo ship shuttling between Australia and China. His normal 4-month break has long over-run, but while he desperately needs money, he fears he may not be able to leave after a regular 8-month stint on board.
"It's really worrying that I could get stuck because there is no cure for this virus. How will I be able to go home?" he said.
His fears are entirely legitimate. A survey of global seafarers carried out by the International Transport Workers Federation in early June showed that 70 per cent of respondents had been forced to extend their contracts and were working against their will, in an environment undermining their health.
Many spoke about suicide and poor mental health aboard ships and used the language of prisons, jails, forced labour and internment to describe their predicament.
The toll on their families has also been huge, with stranded seafarers missing funerals, weddings, the birth of children, and the chance to comfort isolated loved ones during a global pandemic.
Comments submitted to the ITF were anonymous, for fear of repercussions, and many were full of aching despair. Some warned that accidents were waiting to happen due to stress and fatigue.
"Words are not enough to explain the hardships I've faced. Sometimes I feel I won't survive this period," said an Indonesian seafarer who had been at sea for nine months. "Treat us as human beings."
Another worker from Myanmar said he had been deprived of seeing his two-and-half-month old son. "Of course, I would like to see and touch his skin so much. Now my eyes are full with tears as I am writing this letter," he said.
An Indian seafarer, who had not reached shore for more than a year, warned of burnout. "You guys are waiting for a ticking time bomb to explode. You will not get your cargo and you will have a huge environmental disaster," he said.
While a South African revealed that crew had been shaving their heads after running out of shampoo.
"You let your soldiers repatriate, but you want the men and women who maintain your economic life blood to suffer in depressing, dangerous isolation. Who are you going to call on when you need you trade goods delivered, who will be your seafarers?" he asked.
The disruption to global supply lines has already begun. The ITF this week warned that Australia is facing economic carnage from clogged ports after the crews of two ships around its coasts invoked the Maritime Labour Convention to refuse to keep sailing and force their repatriation.
In an interview, Stephen Cotton, the ITF General Secretary, said the Federation had been working flat out for months with government and international labour bodies to find solutions that would enable crew changeovers that also met strict Covid-19 safety procedures.
The body has called on governments to make practical exemptions on seafarers' travel and transit, including unified action on quarantine on visas, quarantine procedures and chartered flights.
Cotton said it was a "logistical nightmare," adding: "I feel like we need an intergalactic agency on top of everybody to make a decision and make it happen."
He called out the "massive disconnect between the ability of shipping to be utterly crucial to fight Covid, whether it be pharmaceuticals, medical hardware or foodstuffs," with the treatment of crew.
"The seafarers are beginning to believe no one cares," he said. "There are a lot of very angry, frustrated, dare I say, emotional seafarers who are questioning society's respect for them," he added. "These folks are first line heroes, let's make sure we don't forget them."
Back in Manila, as he waits in a hostel run by Catholic charity Apostleship of the Sea, Mark, 33, a father-of-two, knows that his family's road to economy recovery will be a long haul when he finally rejoins his ship's engine room.
"My savings are already gone. I have due payments for my car loans and it's very stressful," he said. "Normally I work nine months. Hopefully I will go this time for much longer so that I can cover up the expenses."