Envisat image of a patch of Sargassum

A patch of Sargassum - free-floating seaweed often referred to in nautical lore for entangling ships - captured on 4 September 2008 by Envisat's MERIS instrument off the eastern coast of the United States in the North Atlantic. The patch is centred at 35°45'N and 66°21'W and is about 45 km across.