At 66, Hong Kong diver Harry Chan Tin-ming could be seeking a serene life after retirement. But instead, he is fighting a war against what he calls the oceans’ silent killers – ghost nets, or abandoned fishing gear that trap marine life. About twice a month, Chan, a hearty, grizzled man with an energy that belies his years, dons his dive suit and dips down into the waters, hunting for nets that endanger not only animals but humans. With 30 years of diving experience under his belt, Chan intends to raise public awareness of the impact of ghost nets, and inspire more people to join his cause. “If others see me cleaning the ocean, they would probably think: ‘An old guy can do it, why can’t we?’” he says. Hong Kong is home to a wide diversity of marine life, with some 6,000 species living in its waters, according to conservation body WWF Hong Kong. The number of native marine species per unit area is several hundred times higher than in many other parts of the world. However, marine litter is a constant blight on all this. Ghost nets, with other abandoned or lost fishing gear including lines and hooks, are on the top 10 list of the most commonly found marine litter in Hong Kong, according to a 2016 survey by WWF. They are left tangled on rocky reefs or adrift at sea, trapping fish, dolphins, sharks and other creatures. Human divers, including Chan, have also fallen prey to the nets. In the most serious cases, inexperienced swimmers can drown. As such, Chan, an avid lover of marine life, wants to make the city’s waters clean and diver friendly. Since retiring from the trade industry he has been hunting ghost nets for the past five years, and has conducted some 150 clean-up dives, collecting about 80 tonnes of the material from local waters. But Chan knows one man’s efforts are not enough. Over 17 million pieces of plastic waste flushed into sea via Shing Mun River yearly Unlike plastic waste, which gets more attention, the city’s marine pollution was ignored until Typhoon Mangkhut last September – the most intense storm on record for Hong Kong – washed tonnes of litter on to the city’s shores, according to Chan. “Not many people are aware of marine pollution because much of the litter is under water. That’s what I’m working on – to raise public awareness.” Hidy Yu Hiu-tung, 31, another seasoned diver, is well aware of the hidden problem. Almost quarter of plastic bottles washed up on beaches come from Coca-Cola The dive instructor, who has with 13 years’ experience, says she has observed the marine environment deteriorating not only in Hong Kong but around the world. “When I started diving 13 years ago, it was so beautiful under water. But last year when I dived in the Maldives and Australia, I found dead coral reefs everywhere.” Yu and her husband Willian Lau, also a diver, are among those inspired by Chan’s work and have joined him in his quest against ghost nets. But the task can be challenging and sometimes risky. On a clean-up dive off Stanley Bay last Sunday, Chan and the “ghost net warriors”, his nickname for volunteers, met heavy rain. The downpour rocked their small boat, and the choppy sea made it hard for them to balance in the water. With low visibility beneath the waves, they spotted a 100 sq ft fishing net tangled among the coral, but were unable to remove it in the rough conditions. After an hour, with oxygen running low, the group marked the location and left to resume their fight another day. Because of the risks, marine conservation experts warn that taking on ghost nets should only be done by experienced divers with proper training. Seas swamped in microplastics from city’s obsession with unnecessary packaging Apart from independent groups such as Chan’s, the government and conservation bodies have also been tackling the problem. A specialised team of divers from the Agriculture, Fisheries and Conservation Department have been retrieving ghost nets from Hong Kong waters. To encourage local divers to join the efforts, WWF has launched a programme called “ECF Sea Without Litter II – Ghost Gear Detective”, which trains divers to record sightings of abandoned fishing gear during their normal dives, says Anniqa Law, Oceans Conservation project manager from the environmental group. “We believe that the less time a net is in the water, the fewer chances of it entangling and killing marine life,” Law says. As for Chan, having dived in more than 20 countries including popular hotspots such as the Maldives and Thailand, the waters around home are still where the heart is. “Hong Kong is fun for diving. As a ghost net hunter, you can enjoy diving while protecting the ocean,” he says.