A thick layer of slime engulfs boats moored in the Sea of Marmara, to the south of Istanbul.
Warm water temperatures and industrial waste have been blamed for this record build-up of algae - locals have never seen anything like it.
"For instance the other day, just there, I saw 20-30 shrimp on top of this sea snot,” says one fisherman. "All dead. They had jumped up and got stuck, they couldn't go back down in the water."
The spread of the sludge has now become a political issue, with Turkish President Recep Tayyip Erdogan promising tougher controls on industrial waste.
"We will save our seas from the mucilage calamity, starting by the Marmara Sea,” he said. “My fear is that this spreads to the Black Sea. If it enters the Black Sea as well as Marmara, it will be a big problem. We must take steps without delay. Of course, the increase in seawater temperature due to climate change has played a part."
Critics of the government point out that it has yet to sign up to the 2015 Paris agreement on tackling global warming.