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Workhorse of the sea

Built as the world’s first deep-ocean submersible, the human occupied vehicle Alvin can dive as deep as 4,500 meters (almost 3 miles), giving it access to some 63 percent of the global ocean floor. Alvin completed its 4,500th dive on Feb. 15, 2009, off the west coast of Costa Rica. Launched in 1964, the sub’s most famous exploits include exploring the first known hydrothermal vent sites in the 1970s and surveying the wreck of RMS Titanic in 1986.
(Photo by Dan Fornari, Woods Hole Oceanographic Institution)