Citizens plead to authorities to address the pollution problem as water from a sewage pipeline mixed with seawater in Florya, a crowded beach on Istanbul’s European side.

The seawater turned brown in one spot across the long beach as a drain cover leaked untreated water into the sea, emitting a strong stench. Municipality crews partially shut down the beach but media outlets reported the dirty water was still flowing into the sea. "This is dangerous for everyone. There are swimmers of all ages here but I wonder if they would take measures against this," Hamdullah Öter, a swimmer, told Anadolu Agency (AA) on Sunday.

Seawater pollution was in the spotlight last year when the notorious sea snot, or marine mucilage, engulfed the Marmara Sea to which Istanbul is littoral. The mucilage was cleaned up after an intense campaign but the pollution still haunts bodies of water in Istanbul, something blamed on a lack of action by the city’s municipality.