Nope, it's not one of those newfangled, man-made swimming pools.
This is Brazil's Lençóis Maranhenses National Park, on the country's northeast coast -- and to us, it just looks like one big, natural water park. The park's white-sand dunes (some tower up to 130 feet high when conditions are right) are speckled with crystal-blue lagoons, which form tropical playgrounds in what otherwise looks like total desert.
The lagoons can swell to 10 feet deep and 87 degrees Fahrenheit, making them swimmable during certain times of year. They're expansive, empty and open for human exploration.
Lençóis Maranhenses is too rainy to be considered a technical "desert" -- it gets too much rainfall which results in these fabulous lagoons that well up in nooks and crannies of the park's 383,000 windswept acres.
Some lagoons fill with fish that swim in from the two rivers that traverse the park. Birds and turtles abound, and swimming is allowed in some pools that are deep enough. You're free to hike and bike the park's expanse -- it's recommended to go with a guide so you don't get lost in what visitors call the surreal, desert-like landscape.