Each coral reef is an underwater city. These diverse ecosystems take centuries to build as calcium carbonate exoskeletons collect over time, reaching higher and higher into the saline sky.
The result is both massive and fragile, a wild world housing tens of thousands of creatures great and small, from sea turtles to sea anemones. And once you’ve dove into the water, your snorkeling gear pressed tight against your face, you become an ardent tourist of that city, wide–eyed and buoyant as you watch its inhabitants dart past with elegant precision.
Here are five of the world’s most mesmerizing reef systems for you to explore.