The Sargasso Sea is the only sea without a coastline, located within the North Atlantic Ocean.
Instead of being bordered by land, the Sargasso Sea is defined by ocean currents. 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. These currents create a large circular system known as the North Atlantic subtropical gyre.
The sea is named for Sargassum, a floating brown seaweed that forms distinctive mats at the surface. Christopher Columbus described encountering the seaweed during his 1492 voyage, and sailors once feared that dense vegetation could slow or trap ships. The Sargasso Sea is ecologically important for young eels, sea turtles, seabirds, and other marine life. Its boundaries shift with ocean conditions, so it is a region rather than a sharply mapped body of water.