Bubbles of foam floating on the surface of dark water in the river North Esk in Scotland swirl together to form a constantly changing pattern where the faster current meets a still section of water

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