What is the only sea with no land coastline?

The Sargasso Sea is the only sea with no land coastline.

Instead of being enclosed by shores, the Sargasso Sea is defined by ocean currents in the North Atlantic. The North Atlantic Current, Gulf Stream, North Atlantic Drift, and Canary Current form its approximate boundaries. This makes it a distinctive example of a sea identified by water circulation rather than surrounding land.

The region is named after Sargassum, a floating brown seaweed that forms large mats on the surface. Portuguese sailors encountered the seaweed during Atlantic voyages and gave it names related to grapes because its air bladders resemble small berries. The sea is also an important habitat for young European and American eels, which migrate there to reproduce.

The Sargasso Sea’s position and size are not fixed like the borders of a country. Currents shift, and different sources draw its boundaries somewhat differently. It should not be confused with the Caribbean Sea or the Mediterranean, both of which are bounded by land.