The Sargasso Sea is the only sea with no coastline, being defined by surrounding ocean currents.
The Sargasso Sea lies in the North Atlantic Ocean and is bounded by a rotating system of currents rather than by land. Its approximate boundaries are formed by the Gulf Stream to the west, the North Atlantic Current to the north, the Canary Current to the east, and the North Atlantic Equatorial Current to the south. Because these currents shift, the sea has no fixed shoreline or universally constant outline.
The region is named after Sargassum, a floating brown seaweed that forms large mats on the surface. Portuguese sailors reportedly encountered the seaweed during Atlantic voyages, and the name is linked to the Portuguese term sargaço. Sargassum provides habitat for organisms including juvenile sea turtles, crabs, shrimp, and fish.
The Sargasso Sea is often confused with an ordinary geographic sea bounded by coasts. Its defining feature is oceanographic: currents create a broad gyre that concentrates floating material. The Bermuda Triangle lies within or near the western part of the broader Sargasso Sea region, but the two terms are not synonyms.