Which sea is the only major sea without a land boundary?

The Sargasso Sea is the only major sea without a land boundary.

It is a region of the North Atlantic Ocean defined by ocean currents rather than coastlines. The sea is bounded approximately 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.

The Sargasso Sea is named for Sargassum, a floating brown seaweed that forms large surface mats. Portuguese sailors noticed the seaweed in the fifteenth century and called the region after it. Unlike kelp attached to the seabed, Sargassum can reproduce and complete much of its life cycle while floating.

The region is also important to the life cycle of European and American eels, which migrate there to spawn. The sea’s boundaries shift with changing currents, so it is not a sharply outlined body of water on a standard map.