Bubbles of foam floating on the surface of the water in the North Esk river in Scotland slowly swirl towards the camera and into a shallow plane of focus with a moss covered cliff in the background

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