danger dangerous fast flowing obstacles posts rapid rapids stream turbulence turbulent water waves blue cloud current flow forest lake natural nature new zealand sky Taupo tree Waikato River water resources watercourse Huka Falls cumbria England english fell fellside Great Britain landscape mountain Natural landscape rocks view bridge cold december frost ice park snow trees walk winter aeration channel dam outflow race steps Sussex backdrop background orange red ripples river rust sand sediment sunlight texture yellow abstract effects elegant fill float gentle graphic hades hell hot illustration lava magic melt mystical peace reflection refraction shiny sleep summer tide warm wavy bubbles calm cascade drain lichen moss rock tranquil trickle waterfall