Rob Wilson checks his dive watch and stands up in his cumbersome dry suit, twin oxygen tanks strapped to his back. His buddies are already in the water - two free divers who’ll stay at surface level and keep an eye on things, and two scuba divers who’ll help him recover the ghost net that descends like a pillar, 46 feet to the ocean floor. He steadies himself then giant-strides into the cold Southern Ocean water.

Wilson runs Ghost Fishing New Zealand (GFNZ), a Wellington based volunteer organization that’s dedicated to removing ghost gear and other debris from coastal waters. He and his team head out most weekends on clean up missions, responding to reports of abandoned nets spotted by divers or boats.

45 minutes later, Wilson and his team bob to the surface. They’ve managed to pull the net free from the ocean bed and now set about dragging it laboriously onto the Seafarer II, a 50 feet long commercial fishing boat the volunteers use in their salvaging operations. The net is heavy with mud, encrusted with crustaceans, starfish, sea squirts, and the skeletons of creatures that trapped themselves in the net’s fine nylon filaments. Back on board, the divers free as many critters as they can from the net, tossing them back in the water.

“That’s a 40-50 meter net,” Wilson says, pulling off his dive mask. “It’s probably been down there for at least 20 years.”

Ghost gear - lost and abandoned fishing nets and other fisheries equipment - accounts for around 10 per cent of all the plastic waste in our oceans. As much as 50 per cent of the Great Pacific Garbage Patch is ghost gear. Industrial ghost nets can be massive - up to six miles long. They drift on ocean currents, continuing to catch fish and other marine animals long after their owners lost or disposed of them.

Unless it’s been incinerated, pretty much all the plastic ever produced is still out there in the environment. Nylon nets can take centuries to degrade. They kill everything from shrimp and starfish to turtles, sharks, dolphins, and whales - at an annual rate that is well into the millions. Small fish get trapped, larger fish try and feed on them and get trapped themselves, until eventually the net sinks to the ocean floor where it is picked clean. Then it rises to the surface and the whole cycle begins again. The United Nations Environment Programme (UNEP) estimates that 640,000 metric tonnes of ghost gear enters the ocean ecosystem every single year.

Recovering this ghost gear isn’t easy. Even a net 130 feet long can prove challenging. “It’s tough technical diving, especially right now in the middle of winter when we have to deal with cold water and low visibility,” Wilson explains, as the skipper weighs anchor and prepares to head back to port. We are in the relative shelter of Mahanga Bay on the Miramar Peninsula - a promontory in the middle of Wellington Harbour, but the water is choppy nonetheless, whipped up by powerful gusts from the north. Wellington is known for its winds.

The skipper hoses the net down before we get back to port, washing off years of encrusted mud and dead biomass. Once he’s done, all that remains is a mass of green webbing that seems untouched by its decades long sojourn underwater.

GFNZ cooperates with Healthy Seas, an environmental initiative that connects with volunteer divers from around the world, as well as engaging the fishing industry to both recover ghost gear and develop more sustainable fisheries so that gear isn’t lost in the first place. They are also working with educators so that in the future, closed loop systems can be applied across the industry, from fish farms to open ocean fisheries. One of the organization’s biggest successes has been in finding a market for the nets that are recovered. “Before Healthy Seas came along, the nets were just ending up in landfill, which isn’t ideal,” says Wilson. “Now they’re being recycled.”

The Healthy Seas initiative was co-founded by Aquafil, an Italian nylon manufacturer building circular supply chains that source raw materials from waste instead of directly from the petrochemical industry. The chemical structure of nylon 6 allows it to be infinitely recycled without ever losing its original quality. Aquafil has developed a process that turns nylon based products such as old nets and used carpets into a premium quality patented thread called ECONYL, used to weave Prada’s regenerated nylon fabric and create the new Prada Re-Nylon capsule collection.

Since its inception in 2013, Healthy Seas has collected almost 550,000 tons of nets from the seas and the ocean. Though this represents a small fraction of the amount of net that’s out there, it is still significant, given that recovery operations rely almost entirely on the efforts of volunteers like Wilson and his crew.

We connect with Wilson the next day at his base of operations - a bungalow in the hills above Wellington. His garage is filled with dive gear – tanks, buoyancy jackets, and scooters that can propel divers at high speed through the water. He’s also kept mementos from previous dives - a rusted camcorder from the nineties, tankards and ceramic bottles dating back to the nineteenth century. There’s even a naval captain’s hat.

Inside the bungalow is the computer console where Wilson peers at maps and GPS coordinates: to recover nets, you have to find them first - it’s taken him two weeks and multiple dives with scooters to find this one, since it had drifted from where it was first spotted. Nothing about what Wilson and GFNZ does to recover nets is easy, so what is it that drives Wilson to do this important work?

“I love the ocean. Ghost nets are so destructive - it’s just good to be part of a community that’s doing something about them.”