This aerial photograph taken on May 30, 2021 shows mucilage, a thick, viscous fluid produced by phytoplankton, in Turkey's Marmara Sea at a harbor on the shoreline of Istanbul. The mucilage has been informally referred to as “sea snot” and was first documented in Turkey's waters in 2007. Experts warn the mucilage will occur more often because of global warming. (Photo by Yasin Akgul/AFP Photo)
