When Rob Arnold and a dozen volunteers picked up some six million pieces of plastic debris in a single day from a beach near his home in Cornwall in Southwest England recently, much of it had been floating in the ocean for up to 20 years — like little plastic flippers from the great Lego spill of 1997.

He posted a photo gallery on his Facebook page, and by Saturday the images had gone viral, via Reddit.

“Yeah, it’s got a bit nuts hasn’t it?” Arnold tells Inverse of the reaction to the photos he posted on Facebook. “It’s taken me by surprise really. It was just something I’ve been sort of working away at, plugging away at, and I thought, ‘I’ll just put it on, someone might be interested.’”

These plastic bits of crap on this beach can last for hundreds of years. Rob Arnold

Arnold, 59, is a Cornwall native who remembers the Lego pieces showing up on the beach in 1998 during walks with his son.

Mario Cacciottolo, writing in a 2014 story for BBC News Magazine, describes what happened:

…353,264 plastic daisies dropped into the sea on 13 February 1997, when the container ship Tokio Express was hit by a wave described by its captain as a “once in a 100-year phenomenon”, tilting the ship 60 degrees one way, then 40 degrees back.

As a result, 62 containers were lost overboard about 20 miles off Land’s End — and one of them was filled with nearly 4.8 million pieces of Lego, bound for New York.

No-one knows exactly what happened next, or even what was in the other 61 containers, but shortly after that some of those Lego pieces began washing up in both the north and south coasts of Cornwall. They’re still coming in today.

Ironically, many of the Lego pieces seem to be nautical themed, like those flippers.

It’s not just Lego though, it’s everything. And it’s gotten worse since the ‘90s.

“We’d call it ‘beach treasure,’ and it took us a few years to fill a biscuit tin of these interesting little bits of ‘treasure,’ but now you can go down on the beach and you could fill a van with this stuff,” he says.

Here’s how Arnold explains the massive quantities:

35 bags of mixed plastic collected by myself and volunteers.

Washed and sorted in my separator to remove sand, seaweed, and large pieces of litter, producing 28 bags of mixed plastics, some wood and polystyrene pieces up to 50 millimeters in size, spread out in the sun to dry.

Then sieved into 3 batches by size; 10 millimeters and above, 6-10 millimeters and less than 6 millimeters (microplastics). The term “microplastics” has been adopted to mean pieces 5 millimeters or less, often confused with microbeads, which are actually the very small, almost microscopic pieces used in facial scrubs and toothpaste.

This sieving process produced 13 pillowcases of particles of less than 6 millimeters and a similar volume of the larger sized pieces.

The contents of the 13 pillow cases were further dried, then the lighter polystyrene and wood particles were blown out of the mix, producing 7 bags of approximately 3.5 million of true microplastic particles, plus 5 bags of wood polystyrene mix.

At each stage of the process, items of interest and treasures were spotted and taken out for categorizing later.

Arnold had organized the plastics — many Lego pieces, but there are toy soldiers, golf tees, bottle caps, cigarette holders, and fishing beads — in a project he’s dubbed “the big microplastic sort.”

Arnold describes this photo as such: "Lego from the 1997 container spill — flowers, cutlasses, spear-guns, aqua lungs, a witch's broom, and a few doo-dahs (the little connector pieces from the plastic mold)." Rob Arnold

The sorting process revealed patterns that would be impossible to notice otherwise, like the emergence of Lego flippers.

“The 240 Lego flippers: Normally if you go along the beach you might be lucky to pick up a flipper, but because of the way I picked up this stuff and sorted it and separated it, they appeared after the event, after the collecting of the plastic,” he says.

Adrift for 20 years, they washed up last month.

A hub for the years-long clean-up project has been on the Facebook page “Lego Lost At Sea”, operated by British writer and beachcomber Tracey Williams.

“I feel like we’ve got a little community of people that are interested in things on the beach, because everything you pick up has a story attached to it,” he says. “But also because we are concerned about the problem of plastic pollution.”

This is 20 percent of what was collected on the beach in one day. Rob Arnold

But de-littering the beach is only one part of Arnold’s mission. The other part is using the ugly material to make art that resonates with the public.

“The material I’m using isn’t particularly pleasant material because of the damage it does,” he says. “I like to say all of my sculptures carry the dark message, the tragedy, of what’s happening.”

Arnold on this work: "All the components to construct this piece were found over the last year on my regular beach cleans. Most parts are exactly as found, with little or no further shaping. You may recognize some items." Rob Arnold

“The reason I sorted it all was because I was trying to extract all the nurdles, the little pellets,” he says. “I thought we needed to sort those out and to make some kind of statement with them, because there’s just so many in the ocean.”

“I thought if I could separate them and make some kind of artwork with them to alert the public and also shame the plastics industry to the fact I was able to collect probably four million of these things now, these [nurdles].”

Tregantle Beach, where some 6 million pieces of plastic and other debris were recently scooped up off its shores.

His washing and sorting was aided by a machine (built from stuff he found on the beach and parts from a local swimming pool company) that floated the plastics in water, freeing them of debris before he dried them.

A series of maps published in 2015 show that the Lego pieces have washed up on other shores, too: Ireland, Texas, and Australia, but, primarily, they’ve made landfall in Southwest England.

Arnold and a mess he'll clean up. Rob Arnold

Arnold says he was motivated to do this work after seeing a short film called Midway, by American filmmaker Chris Jordan, about how the albatross seabird is eating plastic, and it’s killing off the species. “To me, they are like the canary in the coal mine,” he says.

In the near-term, Arnold intends to keep combing the beach. “I’m approaching 60. My occupation, I feel, is this campaign. I’m a campaigner against plastic pollution and an artist. That’s me. That seems to be all I’m doing. It’s taken over my life.”