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

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