An aerial view of children sailing on single-handed dinghy boats of the Optimist international class during a training session as the sea is covered by sea snot, a thick slimy layer of the organic matter also known as marine mucilage, spreading through the Sea of Marmara and posing a threat to marine life and the fishing industry, in Istanbul, Turkey June 13, 2021. Picture taken with a drone. REUTERS/Umit Bektas