George Sarelakos emerges from the sea lugging a giant tire. Another two divers surface — with a shopping cart and a netted bag bulging with a cassette player, cans and lots of plastic.

It takes six more people to heave this all onto the main pier of the Greek island of Poros.

"People throw everything down there that they throw away at home," says Sarelakos, a 39-year-old management consultant. In early 2017, he founded the volunteer diving team Aegean Rebreath, which removes trash from Greek seas. "And because it's under the sea, it's invisible to them."

Marine litter is a global problem that can seem overwhelming. Sarelakos says he's trying to do what he can in his own neighborhood. He points at the sun-dappled Aegean Sea, postcard-perfect on its surface.

"There's litter like every 10 centimeters [4 inches] down there," he says, frowning. "Plastics are everywhere."

The World Economic Forum warns that there will be more plastic than fish in the world's seas in about 30 years. In the Mediterranean Sea, where Turkey and North African countries also dump garbage, 95 percent of waste in the water and on beaches is plastic, the World Wildlife Fund says.

"The plastics debate has more or less the same conflicts and barriers with the climate change debate," says Achilleas Plitharas, a policy campaigner in WWF's Athens office. "We all know how bad things are but at the same time we haven't found a common solution, a common path to work on."

Distressed by the proliferation of plastic in seas, the European Parliament overwhelmingly passed a ban last month on what are known as single-use plastics, which include cups, cutlery and straws. Member states must now decide if they want to adopt the ban, which would go into effect in 2021.

Greece has the longest coastline in the European Union and one of the worst recycling rates. A recent EU report showed that Greece recycles only 17 percent of its waste, the second-worst rate in the bloc, which wants member states to recycle half their waste by 2020.

Greeks also use a lot of plastic. To-go freddo cappuccino and frappé drinks come in plastic cups with plastic straws. Vendors at the open-air markets where nearly all Greeks shop for produce pack up fruits and vegetables in plastic bags. Greece's Research Institute of Retail Consumer Goods estimates the average Greek uses more than 300 plastic bags per year. The European Commission estimates that a Finn uses just four. Plitharas says only about 10-12 percent of plastic in Greece is recycled, one of the lowest levels in the EU.

Greece started charging 4 cents for plastic bags in supermarkets this year to cut their use. Municipal authorities also encourage recycling by adding more bins for plastic, paper and glass. These bins, which are blue, often contain items that baffle Kostas Verganelakis, who manages WATT, a private waste management company that collects and sells recyclables.

"I mean, on one island we found the corpse of an endangered sea turtle in the blue bin," Verganelakis says, shaking his head in disgust. "In Athens, we see a lot of organic waste and also items that cannot be recycled, like fireworks, which have on a couple of occasions gone off in our facility and started small fires."

WATT receives approximately 250 metric tons of waste from the blue bins every day. About 12 percent of this is plastic.

"If our plant was not here, then all this waste could go to the landfill," he says, walking past towering hills of plastic bags, bottles and caps.

On Greek islands, a lot of plastic ends up in the sea. Fran Vargas-Bianchi and Daphne Marneli, a Spanish-Greek couple living in Athens, were shocked at how much they accumulated while vacationing on the island of Serifos a couple of years ago. They brought the plastic waste back to Athens because they couldn't find recycling bins on the island.

"People have not yet gotten into the habit of recycling," Vargas-Bianchi says. "People don't see its importance."

He and his wife want to show Greeks that plastic can be put to good use. So they opened a small shop, Plastikourgeio, where they have melted down plastic into heavy bricks that resembles marble. "We make furniture with it," Vargas-Bianchi says, "and also this" — he holds a replica of a Cycladic statue — "that's been really popular."

The store also sells plastic alternatives — edible straws, bamboo cutlery, rice husk coffee cups.

Back on the island of Poros, the Aegean Rebreath divers unload another garbage haul from the sea — aluminum cans, car batteries and more plastic.

They only half-joking call themselves the trash collectors of the sea. Sarelakos estimates the 15-member diving team has gathered about 15 tons of waste from the seas in the last 18 months.

"You know, when we dive, we see parts of plastic bags, almost turning into microplastics and floating around," says Sarelakos, the lead diver. "Fish eat this. ... Whatever we throw into the sea, [it goes] back to our stomachs."

Elina Liarou, a marine scientist who works with Aegean Rebreath, is cataloguing the trash before a municipal crew gathers it to send back to Athens for recycling and what's known as upcycling, which involves reusing recyclable waste in creative ways. "We're spreading it out here on the pier while we sort it out," she says. "Lots of people are walking by. Seeing what's in the sea really shocks them."

Nikoletta Karadima, an 84-year-old Poros native, gasps when she sees what the divers have recovered.

"We're throwing all that down there?" she says, dropping her (cloth) bags of vegetables. "I've got to go grab some people here by the ear! I throw the fish my leftovers from dinner sometimes but this, all this garbage is going to poison them!"

She sits on a park bench in front of the trash and looks over the pier at the sparkling bay.

"That's our sea," she says. "I swim in that sea."

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