According to Wikipedia, up to 100 billion gallons of saltwater rushes from the Saltfjord through a narrows 150 m wide and 3 km long into the large Skjerstadfjord. The water reaches speeds of 20 knots (about 23 mph), and the vortexes formed in the swirling currents can measure 10 m in diameter.
Photographer Magnus Lundgren ponders: "The wild and furious currents in Saltstraumen are going here and there and sometimes up and even worse down. Is the hazard of shooting in this rock'n'roll water compensated by the fantastic environment and subjects?"
Photo credit: Wild Wonders of Europe