The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite captured this image of the Great Blue Hole and Lighthouse Reef in the Caribbean Sea on March 24, 2009. The Great Blue Hole appears at the center of the image, surrounded by a ring of lighter color caused by elevated coral. In fact, parts of the ring surrounding this feature actually crest the water surface at low tide, but a layer of shallow water covers most of Lighthouse Reef Atoll. Boats leave tiny white tracks on the nearby water surface, and two boats appear to travel away from the Hole in this image. East of the boats, a broad band of aquamarine indicates an area of especially shallow water along the reef’s margin. Along its easternmost edge, the reef crests the ocean surface, where breaking waves from the Caribbean Sea form a jagged line of white.

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