Swirling bubbles of white foam slowly float on the surface of dark, black water in a Scottish river in a hypnotic, constantly changing pattern where the faster current meets still water

ripple dissolved organic carbon pollution flowing turbulent water surface river swirling stream foamy whitewater foam fresh water spume river esk north esk carbon froth reflection shifting float foaming flow floating surge detergents movement swirl circulate drift patterns bubbles dark bubble spiral twist contrast slow change black hypnotic fishing white eddy current fast salmon organic