The Sargasso Sea is the only sea without a land coastline, defined instead by ocean currents in the North Atlantic.
It lies within the North Atlantic Subtropical Gyre, bounded approximately by the Gulf Stream, the North Atlantic Current, the Canary Current, and the North Atlantic Equatorial Current. These currents form a broad rotating system that encloses the sea.
The region is named for Sargassum, a floating brown seaweed that forms large mats on the surface. Unlike many seaweeds, Sargassum can complete its life cycle while drifting in the open ocean. Its habitat shelters young fish, sea turtles, seabirds, and other marine life.
Christopher Columbus reported seeing floating vegetation during his 1492 voyage, and sailors later developed many myths about the area. The Sargasso Sea has no fixed shoreline or universally agreed boundary, so its size changes with the definition used. It is a geographic and ecological region rather than a country or administrative territory.