On November 22, 2017, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this natural-color image of discolored water along the Adriatic Sea coast of Italy and the Balkans. It is possible that the milky color of the sea comes from a massive bloom of phytoplankton. But the close proximity to the coast, the extent and pattern across such a wide area (including the opposite coastline), and the coincidence with heavy rainfall and cyclonic storms in the region all suggest that the color comes from suspended sediments carried out by rivers or stirred up from coastal shallows by strong winds.
NASA Earth Observatory image by Joshua Stevens, using MODIS data from LANCE/EOSDIS Rapid Response. Caption by Mike Carlowicz.