The Sargasso Sea Is the Only Sea that Lacks Land Borders.

The Sargasso Sea is the only sea in the world that does not have land borders. Instead, it exists entirely within the Atlantic Ocean. It is home to a free-floating seaweed called Sargassum (for which it is named) and its borders are defined by ocean currents. It is banded 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 they are defined by ocean currents, its borders are dynamic, although they roughly correlate with the Azores High pressure center.