The Only Sea on Earth That Does Not Touch Land

Far out in the North Atlantic, about 590 miles east of Florida, lies a patch of unusually calm water - it's the only sea on Earth with no shores.

Sargasso Sea

Strong currents rush around its edges, but inside the ring, the surface settles into long, smooth swells. This region has no coastline or islands, yet it has a name: the Sargasso Sea, a part of the ocean that behaves differently from the water around it. At the surface, golden‑brown seaweed called Sargassum gathers into loose mats. Tiny gas‑filled bladders keep the seaweed afloat, so it rides the waves instead of sinking.

The Sargasso Sea is a unique region in the North Atlantic Ocean, defined not by land but by swirling ocean currents, famous for its vast mats of free-floating Sargassum seaweed, creating a "golden floating rainforest" that supports diverse marine life, serves as a crucial habitat for turtles and eels, and acts as a migratory stop for whales, all while being the only sea with no land boundaries.

Shrimp, bright juvenile fish, pale crabs, and many other creatures move through this tangle, using it as food, shelter, or both. The Sargasso Sea is the only sea named after a plant rather than a coastline. European and American eels begin their lives beneath Sargassum mats as transparent larvae. They ride the ocean currents westward or eastward, depending on the species. Indeed, it was not until 2023 that the migratory journey of European eels was finally unravelled.

The Sargasso Sea Commission, created in 2014, calls this region a “haven of biodiversity” and asks countries to route ships around the densest Sargassum mats and consider marine protected areas. If the Sargasso Sea lost its special conditions, rivers from Newfoundland to the Gulf of Mexico would send eels to the ocean only for them to search in vain for a birthplace erased by heat.

For something that looks like an empty patch of blue on a map, the Sargasso Sea plays a large role in Earth’s climate and marine life.

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