The Sargasso Sea is the only sea without a coastline, because ocean currents define its boundaries in the North Atlantic.
It is enclosed broadly by the North Atlantic Current, Gulf Stream, North Atlantic Equatorial Current, and Canary Current. Unlike ordinary seas, it has no surrounding land boundary. Its location and outline can shift with changing currents, so maps usually show it as a large oceanic region rather than a sharply fixed shape.
The sea is named for Sargassum, a floating brown seaweed found in abundance at its surface. Sargassum provides shelter and habitat for young eels, turtles, fish, and other organisms. The region is also important to the life cycle of the European and American eels, which migrate there to spawn.
The Sargasso Sea is sometimes confused with the Bermuda Triangle because both are associated with the western North Atlantic. They are not the same region, and the Bermuda Triangle is not an officially defined oceanographic sea.