"Most of the victims are men and boys from poor, rural areas in Cambodia and Myanmar. Usually they are approached by someone they know, or a friend of a friend, and offered work in Thailand. They are told the jobs are on shore - perhaps in construction or on a farm - and assured of a generous wage. Trusting the broker, they contribute a small amount of money to help with travel costs, and commit to pay the balance later. The broker will transport them to the Thai border.

"After crossing the border they will be hidden in a truck and - instead of being taken to the job they were promised - they'll be delivered to a fishing port. They don't read or understand Thai, they have no idea what's going on, and suddenly they're being controlled by a gang of toughs working for a trafficker. They'll be presented to a boat captain at the pier who will purchase them; literally purchase them. Depending on how strong they look, the price usually ranges from 12,000 to 25,000 baht [HK$2,700 to HK$5,700].

"The captains first seek crew willing to sign on voluntarily, but frequently struggle to recruit enough people because these jobs are so unattractive. So the captains or boat owners will call their contacts in the port communities. They have long-term relationships with locals who might, for example, run a karaoke bar but also dip into trafficking, or who are known as brokers of migrant workers. It's a 'no questions asked' system, backed up by local government officials and police who are paid to look the other way and sound the alert if a crackdown is imminent.

"There are also instances of Thais being trafficked on boats. One guy I interviewed - who had a serious problem with alcohol and had fallen out with his family - had been drinking in a public park in Samut Sakhon, a major port area. He passed out on the ground and woke up at sea. When the boat returned to land a couple of months later, he escaped. But then he went back to alcohol and, a year later, the same thing happened again.

"[Or sometimes], a young Thai man, newly arrived from a rural area and looking for work, will be approached by a taxi driver who offers to help. He'll be driven to a house, locked inside by a gang and later sold to a fishing boat. The taxi driver is paid a finder's fee. Or he might meet a recruiter who pretends to be his friend. They'll go to a karaoke bar to drink, sing and enjoy the company of women. Dawn comes and the bar owner - in cahoots with the recruiter - presents a bill with hugely inflated prices. He'll threaten violence if he's not paid but will offer the victim a chance to clear his debt - by signing on to work on a fishing boat.

"Once on board, the crew are forced to work long hours, up to 22 hours a day. If they don't work hard enough, or make mistakes, they are beaten with fists and clubs, or whipped with stingray tails. I've spoken to many fishermen who have seen fellow workers shot and killed by the captain, or thrown overboard while still alive, because they did something wrong, or were too sick to work.

"It's a very, very dangerous environment to work in, especially for people who are totally exhausted. Men lose their fingers or arms in winches that have no safety guards. Crew members are also forced to sort the fish in holds below decks, where it's extremely cold and deadly gases can build up to such levels that they may pass out or suffocate. There's no medical care on board so some survive, some die.

"They go for weeks without showers, eat the same poor-quality food every day and sleep in extremely cramped quarters. Essentially, it's hell on Earth.

"Boats which fish in local waters are likely to return to port within a few months, giving crew the opportunity to escape an abusive captain. But because rampant overfishing has depleted fish stocks, many boats head much further afield. They can stay out at sea for years, using supply ships to deliver provisions and ferry the catch back to Thailand.

"At the end of this living nightmare, the fishermen will hope to make some money. The broker's fee, and the amount the captain paid for them, will have been deducted from their salaries. But no one has a written contract and there's no transparency, so the captains and fleet owners find it easy to cheat [the workers].

"I interviewed five Burmese men who worked on a Thai fishing boat in Indonesian waters for four years. They expected to receive as much as 100,000 baht each - enough to build a new life back home. Instead the boat owner gave them 2,000 baht. When they protested, he brandished a weapon and threatened to call the police and have them arrested as illegal migrants. They weren't even paid enough to cover the journey back to Myanmar.

"This industry involves a sickening amount of greed. The traffickers, captains and fleet owners seize men in the prime of their lives - in their late teens and early 20s, when they're healthy and strong. They suck the life out of them, leaving them physically and mentally damaged; mere husks of the men they once were. It's a type of cruelty that is inexplicably brutal."

Nick Grono is chief executive of the Freedom Fund, the first private donor fund dedicated to ending modern slavery. It aims to raise US$100 million for smart anti-slavery investments in the countries and sectors most in need.

"Three factors combine in a perfect storm to drive extreme exploitation in the Thai fishing industry.

"First is the demand for cheap labour. Fishing is a marginal economic activity because there are too many boats and not enough fish. To boost profits they pay next to nothing for labour, which would otherwise be their biggest operational cost.

"Second is the presence of vulnerable populations - large migrant communities in neighbouring Myanmar and Cambodia that can easily be exploited.

"Third is the weak rule of law. It's illegal to engage in human trafficking and forced labour but the boats aren't inspected rigorously. It's not a priority for the Thai authorities because most victims aren't Thai and there are powerful vested interests that benefit from the trade.

"We're trying to fight this situation by targeting three sectors.

"The first is the Thai government. They're already under considerable international pressure. Last year, the US State Department downgraded Thailand to the lowest tier on their Trafficking in Persons Report, putting them on a par with Syria, North Korea and Yemen. The European authorities have also issued a warning with a threat to ban Thai seafood from European markets unless they crack down on slavery. Thai seafood exports to the US and the EU are worth US$2.5 billion a year, so the impact of an embargo would be significant.

"The Thai government is desperate to have these decisions reversed. They're making a lot of claims and statements, and holding conferences and formulating strategies, but we haven't seen any concrete action yet. No ship owners or captains have been prosecuted.

"Our second target is the corporates - predominantly the Western retailers who are generally responsive to bad press and consumer pressure. There's been a lot of attention on 'trash fish' - undersized or inedible fish that are ground into meal to feed farmed prawns. NGOs and investigative journalists have tracked the prawns to the shelves of the top four global supermarket brands: Walmart, Carrefour, Costco and Tesco. They have strong evidence that the products of slave labour are being sold in these supermarkets. The supermarkets have all acknowledged the problem and made strong statements condemning slavery.

"The problem is that even with the best will in the world, they don't have complete control of their supply chains. They have to decide how hard they can push their suppliers, whether they will accept goods supplied at higher cost and whether they have alternative markets to source from. Responsibility is a grey area and a pass-the-buck approach is inevitable, but now that abuses have been recorded and reported in such detail, there's real scrutiny on these companies.

"We want them to collaborate in pressuring their suppliers because together they have the clout to drive real change. We're calling on them to develop a more sophisticated process in which they set targets and time frames for their suppliers to enact measureable change, or they will take their business elsewhere.

"The third sector is the migrants themselves. They're highly vulnerable people and very little work is being done to support them. Most victims have no idea about their rights. We're funding NGOs in Thailand to provide practical and legal support to those either trapped on boats or cast ashore.

"Ultimately, responsibility for change lies with the Thai authorities. The prime minister, Prayuth Chan-ocha, recently issued a statement saying it's a top priority for the government. On previous occasions, however, he has pressured journalists not to publish damning reports for fear of damaging export earnings. It's essential that we keep up the pressure on the government and the corporates, while making efforts to support the victims of human trafficking."

is a former deep-sea fisherman. He advocates for the rights of migrant workers in the New Zealand fishing industry, where forced labour on foreign fishing vessels is a problem the government is failing to curtail.

"I first got involved in 2010, when a Korean trawler, the Oyang 70, sank off the coast of Dunedin, with the loss of six lives. The tragedy brought to light the terrible conditions on board and the fact that the crew were paid only US$250 a month.

"I travelled to Indonesia to meet the surviving crew and widows. I learned that many of them had been trafficked into forced labour, cheated of their wages, subjected to beatings and, in some cases, sexually assaulted by the ship's officers.

"In a stable first world democracy, that's completely unacceptable. This has been going on for 30 years and it has to stop.

"The problem has arisen because New Zealand fishing companies don't catch their quota with their own boats. Instead, many charter South Korean vessels. Most crew members - like those on the Oyang 70 - come from Indonesia, but there are also men from the Philippines, Vietnam, China and Myanmar. The vessel owners use manning agents to find staff. The agents work with recruiters who live out in the villages, usually in impoverished areas with high unemployment.

"To get a job, crew members have to pay a fee and put up collateral. This could be a motor vehicle, land deeds or house titles. These are the coercive means used to keep them in a bonded labour regime.

"They are presented with a stack of papers to sign. The 'real' contract - the one that meets New Zealand's standards and offers the minimum wage [NZ$14.75/HK$79 an hour] - will be hidden in the pile so they don't spot it. They'll also sign a contract with the manning agent that determines what they'll actually be paid.

"Crew members are subjected to constant verbal abuse and physical assault. We have multiple reports of men being beaten, sexually assaulted or raped, being made to stand in the freezers or out on deck in extreme weather, and having their mouths taped shut for talking.

"They're overworked. We have reports of 50-hour shifts. They get so fatigued they fall asleep at their work stations and are prone to having accidents.

"Foreign charter vessels have also committed environmental crimes - dumping rubbish and oil at sea and practising 'high-grading', in which poorer quality fish are thrown overboard to make room for higher value catches.

"The manning agents will skim the crew's wages for the first few months, as part of their fee. When the men finish their contracts they'll receive the residual portion, which amounts to around 10 per cent of their entitlements under New Zealand law.

"The fishing companies and vessel owners profit from this exploitation, but the system is so complex - with networks of brokers and middlemen - that no one appears accountable. The managers of the fishing companies in New Zealand claim they don't know what goes on, but that appears inconceivable.

"The New Zealand government does little. They say it's a civil matter, but the role of government is to monitor and enforce its own legislation. They're failing miserably at that and, what's more, they're complicit in maintaining the problem. In many cases, fishermen are deported back to their home countries as soon as they step off the boat. This prevents them from claiming wages owed to them and denies them the chance to pursue their rights under New Zealand law.

"New Zealand companies are audited by the departments of Labour and Immigration, so there should be checks in place. But despite evidence that time sheets were falsified, no one has been charged. In terms of providing support, their plan of action has been to advise victims of abuse to 'phone the emergency services'. That's of no use to someone trapped on a ship and who doesn't speak English.

"In spite of the government's failure to act, we are making progress. We've got a number of cases in court, with 450 plaintiffs from 11 vessels claiming NZ$25 million in money owed. These vulnerable migrant workers had a legitimate expectation to be treated fairly under New Zealand law - to the nation's shame, that has not happened."

is a member of the legal team for Slave Free Seas, a New Zealand-based charitable trust that promotes legal strategies to combat human trafficking at sea. He is also a PhD candidate at the University of Melbourne, researching transnational criminal law in relation to human trafficking in Southeast Asian fishing industries.

"Any question of human trafficking has to start with the international legal definition, and that comes from the United Nations Trafficking Protocol.

"According to the protocol, for a crime to have been committed, you need to prove the three elements of the offence - the act, the means and the purpose.

"In cases of human trafficking, the act will be the recruitment, transport, receiving or harbouring of a person. The act in itself might appear perfectly benign. What makes it illegal is that it's done by certain means - coercion, abduction, the threat or use of violence, fraud, deception, or the abuse of power.

"The third element is purpose and that is always some form of systematic exploitation, whether it's slavery, forced labour or sexual exploitation.

"The victims of human trafficking are the linchpins from a legal standpoint. They need to be accurately identified as such because without a victim, in the eyes of the law, you don't have a criminal offence.

"In practice, all responses to trafficking are partly legal and partly political. Governments always try to influence the way the law is applied. That's exactly what we've seen in New Zealand - Indonesian fishermen were trafficked and exploited on Korean-flagged ships with impunity because of a loophole in the law. All the elements of trafficking were clearly identifiable, but the New Zealand government took the view that it was an employment matter, not a criminal one.

"This is very typical. We see similar responses to trafficking situations all over Southeast Asia. Thailand's fishing industry is a prime example.

"Earlier this year, an extensive investigation by Associated Press discovered 4,000 fishermen, from Myanmar, Cambodia and Thailand, in Indonesia's Maluku Islands. They were working for a Thai company called Pusaka Benjina Resources. They had been working 20-hour days without a break, they'd been beaten up, given rotten fish bait to eat, and some had been held in cages on the islands as punishment for misbehaviour. And they hadn't been paid. The company admitted that the men were exploited, but it claims they weren't slaves. It looks like they're trying to manipulate the facts to keep on the right side of the trafficking law.

"So far, 68 Thai nationals have been repatriated, but only nine have been formally identified as victims of trafficking, even though a wealth of evidence shows they could all be considered victims.

"Governments are legally obliged to protect victims of trafficking but by keeping numbers low, they can shirk those obligations and even turn the responsibility onto the victims themselves. If they are not identified as victims of trafficking, the men on the Maluku Islands could potentially be prosecuted, either for fishing illegally in Indonesian waters or for immigration offences, because they don't have legal identity documents. It's absolutely criminal.

"The Rohingya people are a different case in terms of the responsibility of governments. It's well known that many of the boats currently being bounced between Thailand, Malaysia and Indonesia have victims of trafficking on board. The Rohingya pay migrant smugglers in Myanmar a fee to be taken to Malaysia, where there's a large Muslim population. They're deposited in jungle camps on the Thai-Malaysian border and held to ransom. If they're unable to pay they'll be sold off, either as wives or fishermen.

"The Rohingya should be entitled to protection under international refugee law. If the situation worsens, it could be argued that the Thai government's refusal to help becomes a matter for the International Criminal Court, because they're perpetuating the state of trafficking.

"In all these cases there's an urgent need to properly classify victims - those who have been trafficked, those who are smuggled migrants and those who are asylum seekers. Then the obligations incurred by governments, in light of those categorisations, need to be enacted as rapidly as possible to make sure everyone's given the protection they're entitled to under international law."

Victims of slavery at sea speak up

"We tried to flee, but the agent caught us and we were beaten. My friend lost consciousness. Because I covered myself, I did not get hit in the face. But my friend was hit badly."
Than Shwe, 18, from Myanmar, once a fishing crewman in Thailand

"The brokers told me that if I did not want to go, I should look at this gun because I could be killed very easily. They said a bullet only costs 12 baht."
Trafficked fisherman rescued in Kantang, Thailand

"I thought I was going to die. They kept me chained up, they didn't care about me or give me any food … They sold us like animals, but we are not animals - we are human beings."
Cambodian trafficked into the Thai fishing industry

"The worst was when I saw one of my co-workers fall in the sea. We were ordered to continue to work and prevented from helping him. He drowned. That is when I decided to escape."
Burmese victim of trafficking

"I experienced sexual harassment many times on-board Oyang 75. I have never told anyone about this because of my position as a labourer. The perpetrator … was the chief officer on the boat. I often thought about asking for help but I didn't know who to ask."
Andi Sukendar, Indonesian victim of trafficking in the New Zealand fishing industry

"When we berthed at Lyttelton Port [in New Zealand] … the bosun punched me on the chest because I was told to tie the net, but I wasn't sure precisely which part I had to tie. Since then I have always been anxious while working. And when we were at sea, the second bosun often punched the back of my head."
Dameriyanto, Indonesian victim of trafficking

The first four quotes were collected by Thai-based NGO Environmental Justice Foundation