For a few months annually, the Lençóis Maranhenses National Park turns into a fantasy world of bright blue and green lagoons among crescent-shaped dunes enjoyed by tourists and residents.

Resembling its translated name of "bedsheets," the Lençóis Maranhenses National Park in Brazil’s Maranhão state sprawls 40 miles across in a sea of white sand. But for a few months annually, it turns into a fantasy world of bright blue and green lagoons among crescent-shaped dunes enjoyed by tourists and residents.

The phenomenon all starts commonly as two rivers deposit sand from the land's interior on its coast. Then from October through November, the region's forceful winds blow the sand up to 30 miles back inland, creating dunes towering as high as 130 feet.

Though it looks desert-like, Lençóis Maranhenses gets around 47 inches of rain annually falling mostly between January and June. The rain pools up in the dunes' valleys and makes lagoons up to 10 feet deep and 300 feet long. Then as dry season approaches, the lagoons evaporate, losing up to 3 feet of water monthly.

When fullest, lagoons connect with rivers and other lagoons, helping wildlife migrate. The 600-square-mile national park, which sees around 60,000 tourists annually, was started 30 years ago to protect this ecosystem.