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 a still section of water

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