The Only Sea in the World Without a Coast

Caitlin Dempsey


Found in the middle of the Northern Atlantic Subtropical Gyre (a gyre is a large system of rotating ocean currents) near the Bermuda Islands, the Sargasso Sea is surrounded on all cardinal directions by ocean currents.  

The Only Sea Without a Land Boundary

The only sea on Earth without a land boundary, the Sargasso Sea is bounded to the west by the Gulf Stream; on the north, by the North Atlantic Current; on the east, by the Canary Current; and on the south, by the North Atlantic Equatorial Current.

Location map showing where the Sargasso Sea is located.  The base map is a tinted topography map showing the surrounding continents and a blue ocean.
Map showing the general location of the Sargasso Sea. Map: Caitlin Dempsey using Natural Earth data.

About 1,107 km wide and 3,200 km long, the actual boundaries of the sea vary and roughly correlate with the Azores High Pressure Center.

A Holopelagic Specie

Named after the free-floating seaweed genus called Sargassumthe Sargasso Sea is home to a high diversity of marine animals such as white marlin, porbeagle shark, and dolphinfish that use the algae for food and shelter. 

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The Sargasso Sea is home to many migratory fish species, turtles, and crabs.

Sargassum are holopelagic, which means that this seaweed reproduces vegetatively as it floats in the ocean unlike other seaweeds which reproduce and start their lives on the ocean floor.

Where Does the Word Sargasso Come From?

Both Sargassum and Sargasso originate from the Portuguese word “sargaço” meaning grape.  The seaweed was named by 15th century Portuguese explorers  who thought the air bladders of the Sargassum looked like the fruit.

First Map to Show the Sargasso Sea

A map from 1700 showing North America.
L’Amerique Septentrionale 1700. Map: David Rumsey Collection.

L’Amerique Septentrionale published in 1700 by Guillaume De L’Isle is the first map to show the Sargasso Sea. While not named, the Sargasso Sea is showing with the text “herbes flotante sur la mer” which translates to “grass floating on the sea”.

A cropped section of a 1700 map showing in French the notation where the Sargasso Sea is located.
A detailed look at the section that maps out the location of the Sargasso Sea. Map: L’Amerique Septentrionale, 1700.


Ardron, J., Halpin, P., Roberts, J., Cleary, J., Moffitt, R., & Donnelly, B. (2011). Where is the Sargasso Sea. Sargasso Sea Alliance Science Report Series24.

Septentrionalis Map Exhibit. (n.d.).

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About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.