Sargasso Sea: Code Blue by Bryan Walsh, Bermuda

Photo: Shari Sant Plummer

The Sargasso Sea has no shores. The 2 million-sq.-mi. body of water in the middle of the Atlantic is defined by two features: the ocean currents forming the North Atlantic subtropical gyre, which cycles around the sea, and sargassum, the free-floating golden-brown seaweed. The sargassum can be found scattered throughout the sea, sometimes entwined in vast waterborne mats. When Christopher Columbus encountered the sargassum while crossing the Atlantic, he ordered his men to fathom the depths, believing he had struck land. The oceanographer Sylvia Earle, though she prefers not to think in land-based