Scientists have discovered a new type of plastic pollution spreading on rocks in Madeira, which has been dubbed "plasticrust".
Researchers say they have found small patches of what looks like melted plastic encrusted on rocks on the Portuguese island's shoreline.
The plastic patches - which are mostly blue and grey and are of various sizes - were first spotted in Madeira in 2016 but experts say they have increased substantially since then.
Tests have shown the material of the "plasticrust" is polyethylene, the world's most widely used plastic, and it is exposed on rocks when there is a low tide.
Scientists at Portugal's Marine and Environmental Sciences Centre say they are unsure where the plastic comes from or how it could affect marine life.
But they have warned there is now a risk that "plasticrust" could be eaten by sea creatures.
"Plastic debris is one of the most extensive pollution problems our planet is facing today and a particular concern for marine environment conservation," they wrote.
"The potential impact that these new 'plasticrusts' may have needs to be further explored."
Marine life, including corals and important fisheries, is under threat due to the amount of plastic pollution in our oceans.
More than eight million tonnes of plastic is thrown away each year and washed out to sea.
By 2050, the plastic in the world's oceans will weigh more than all the fish, according to The Ellen MacArthur Foundation.
:: Sky's Ocean Rescue campaign encourages people to reduce their single-use plastics. You can find out more about the campaign and how to get involved at www.skyoceanrescue.com