A surfer rides the thunderous “pororoca” tidal bore wave on Amazon river near Caviana island in Marajo in Para State, part of the Brazilian Amazon jungle, June 17, 2011.  The word “pororoca” comes from the Amazonian indigenous term meaning “destroyer, great blast”. The feared and thunderous waves capsize boats and wash away nearly everything in their path twice each day. The phenomenon begins when ocean tides reach the shallow river water flowing out at the mouth and can be heard two hours before arriving, producing waves of several meters, moving at speeds of up to 30km per hour. Picture taken on June 17, 2011.  REUTERS