Lençóis Maranhenses Park, Brazil

Photograph by George Steinmetz, National Geographic

Water dark with tannin inspired the name Rio Negro, or "black river," which swirls across virgin sand in Lençóis Maranhenses National Park. In the park's ponds, thriving communities of algae can turn the water blue or green.

Photo Tip: Aerials can be tricky because you’re moving when you shoot them, so use a shutter speed of 1/250 or faster.

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