To the casual observer these 'rocks' are simply a handful from the hundreds upon thousands of similar examples at Gunwalloe's Church Cove beach, yet in fact they contain a much darker secret.

For while they give off every appearance of being a product of nature, the 'stones' are in fact chunks of plastic - man-made, waxy to the touch and almost impossible to identify due to their close colourings and markings of the real thing.

Falmouth Packet:

This collection was picked up at Gunwalloe on Sunday during a clean up of Church Cove and Dollar Cove organised by the Cornish Seal Sanctuary at Gweek.

Operations supervisor Alex Pearce, who organised the clean up, told the Packet: "They're very, very waxy and light, but they look exactly like rocks. They're amongst others so that you think it is a rock - it's very scary."

Also collected were tiny pieces of plastic known as nurdles, which are used in the production of plastic and are making their way in their millions into the oceans. They break down to even tinier pieces of microplastic and are eaten by fish, making their way into the food chain.

Around 70 people joined the seal sanctuary team to clear the beaches, after Storm Eleanor left even more debris than usual around the coastline.

People off all ages joined in, with many children and even dogs.

Alex added: "There weren’t a lot of big pieces of rubbish during this clean but we are finding an increasing amount of small pieces of plastic, such as nurdles.

"It's when you start looking you realise how big a problem it is,because it's now breaking down and getting into our food chain and in animals."

She described the amount of people at the beach clean as "incredible," saying: "It means people are starting to understand the cure and are more aware. It was fantastic to see that many people out."

The team also removed some netting, which is dangerous to seals, as they can become trapped in it causing serious wounds.

Jana Sirova, the sanctuary's general manager, said: “It is fantastic to see so many people wanting to help marine life; it means the message is getting out there. No matter how big or small, anything you collect from the beach is a positive step towards helping our ocean life."