Dive Into Five of the World’s Deepest Freshwater Swimming Holes

(via Smithsonian) Sinkholes and fissures can form without much warning, swallowing up buildings, highways, cars and anything else in their wake. Many of the planet’s most famous depressions came into formation tens of thousands—even millions—of years ago, eventually filling up with water. The result for overheated summer travelers: a chance chance to cool off surrounded by some pretty cool geology.