The submersible Alvin has achieved certification from the U. S. Naval Sea Systems Command (NAVSEA) for operations to its rated depth of 4,500 meters (approx. 2.8 miles). (Photo by Chris Linder, Woods Hole Oceanographic Institution)

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The submersible Alvin has achieved certification from the U. S. Naval Sea Systems Command (NAVSEA) for operations to its rated depth of 4,500 meters (approx. 2.8 miles). (Photo by Chris Linder, Woods Hole Oceanographic Institution)