This is the only sea on Earth that has no 'shore' because it never touches land

Far out in the North Atlantic, about 590 miles east of Florida, lies a patch of unusually calm water. 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.

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.

Sargasso Sea sailor stories

Long before satellites or ocean sensors, sailors noticed this unusual water. Christopher Columbus described the fear of being becalmed in 1492 when he wrote that the ships might “never again feel a breath of wind.”

The crews did not know that the calm surface hid a powerful system of currents below. They were sailing across the North Atlantic subtropical gyre – a huge loop of water that draws in water from many latitudes.

These currents corral floating material and keep it in place. That pattern helps explain why Sargassum gathers here and why this sea has such a distinct character.

Sargasso Sea plants and animals

From above, the Sargasso Sea looks like an 800-mile-wide plant nursery. Scientists call the drifting mats “habitat islands” because the seaweed provides shade, hiding places, and food sources all in one package at the ocean surface.

Many animals that would otherwise be exposed in the open water can tuck into this cover and avoid predators.

Porbeagle sharks cruise along the dim edges of the mats, while Bermuda storm‑petrels sweep just above the water, grabbing shrimp and small fish.

Surveys have counted more than 100 invertebrate species clinging to Sargassum, living their entire lives on these drifting clumps until the mats finally break apart.

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.

Over time, they grow, change shape, and slip into rivers that can reach as far inland as Indiana, where they may live for decades in freshwater.

When they reach maturity, these eels swim back out to sea and make the 3,000‑mile journey to the Sargasso Sea to spawn once and die.

They return to the same broad region where they started, even though there are no obvious visual landmarks to guide them. This ability still puzzles zoologists.

Calm patch and climate

The Sargasso Sea is also plays a part in Earth’s climate system. In summer, the surface warms to about 82–86 °F; in winter, it cools to roughly 64–68 °F. Warm, salty water moves northward, while cooler water returns south.

This exchange helps steady weather patterns on both sides of the Atlantic by shaping how heat and moisture move through the atmosphere.

The open water also absorbs carbon dioxide from the air, and tiny plankton use that carbon to build shells. When they die, many of those shells sink to the seafloor, carrying the carbon with them and keeping it out of the atmosphere for long periods.

Since the 1950s, researchers near Bermuda have recorded conditions in these waters. The long record shows that, since the 1980s, the average temperature here has climbed by roughly 1 °C, or about 1.8 °F.

Warmer surface layers resist vertical mixing, so oxygen has a harder time reaching depth, and nutrients from below do not rise as easily to feed plankton.

These measurements, combined with data from drifting Argo floats and satellite color scans, make the Sargasso Sea a key site for studying ocean acidification in the open Atlantic.

Atlantic Ocean fish trap

The Sargasso Sea sits at the center of several major surface currents, so today this calm region collects floating debris from across the North Atlantic.

These looping flows pull in plastic bags, bottle caps, and abandoned fishing gear and hold them in the rotating water.

One survey estimated roughly 200,000 pieces of debris per square kilometer – about 518,000 pieces per square mile – spread over several hundred miles.

Underwater microphones pick up the growl of cargo vessels as they cut straight through Sargassum mats. That noise can mask the low‑frequency calls of sperm whales passing beneath, and floating nets tangled in the weed can trap juvenile turtles.

Sargasso Sea climate policies

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.

Governments are also negotiating a treaty to cut plastic pollution at sea and to protect key migratory corridors that pass through or near the Sargasso Sea.

Changes in this “sea without shores” would reach far beyond its boundaries. 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.

Humpback whales might arrive in spring to find feeding areas stripped of their usual prey. Storm tracks over Europe could shift, and the Atlantic might store even more of the planet’s excess 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.

The still water sends a clear message: we need to protect this calm region, or be prepared for more intense and less predictable changes.

The full study was published in the journal Frontiers in Marine Science.

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