It's true, Brazil’s Lençóis Maranhenses National Park harbors a coastal dune field that floods during the wet season, January to May. The park’s creamy sand and sparkling water - rains trapped in ribbons of dunes - shelter nesting birds, turtles, and fish.
Source: http://travel.nationalgeographic.com/travel/365-photos/dunes-lencois-maranhenses-national-park-brazil/
