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Why You Cannot Sink in the Dead Sea: The Science of Extreme Salinity
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Why You Cannot Sink in the Dead Sea: The Science of Extreme Salinity

March 28, 2026 · 4 min read

The Fact

The Dead Sea is so salty that it is impossible for humans to sink in it.

Float on your back in the Dead Sea and you will find the experience unsettling at first — your legs pop up, your feet break the surface, and no matter how you try to push yourself under, the water pushes back. You are not swimming so much as being gently refused entry. This is not a trick of the light or a tourist myth. The physics are real, and they come down to one of the most extreme chemical environments found anywhere on the surface of the Earth.

The Chemistry Behind the Float

The Dead Sea sits at the lowest point on Earth's land surface, roughly 430 meters below sea level, in a landlocked basin on the border of Jordan, Israel, and the West Bank. Water flows in from the Jordan River but has nowhere to go — there is no outlet. As the sun evaporates the water, the minerals and salts dissolved in it are left behind and concentrate. Over thousands of years, this process has produced a body of water with a salinity of approximately 34 percent, compared to roughly 3.5 percent for average ocean water.

That concentration changes everything about how objects behave in it. Buoyancy is determined by the density of the fluid relative to the density of the object floating in it. The human body has a density of approximately 0.98 grams per cubic centimeter — just slightly less than fresh water, which is why most people float but with effort, and sink if they exhale fully. The Dead Sea's brine, loaded with magnesium chloride, sodium chloride, and calcium chloride, reaches a density of around 1.24 grams per cubic centimeter. A human body is simply not dense enough to overcome that upward pressure, no matter how you position yourself.

What "Dead" Actually Means

The name is not metaphorical. At such extreme salinity, almost no multicellular life can survive. Fish carried in by the Jordan River die almost immediately upon entering the hypersaline water. No seaweed, no mollusks, no conventional aquatic life makes its home there. For millennia, ancient observers saw a sea that seemed to kill everything that entered it, and the name stuck.

That said, "dead" is not entirely accurate by modern standards. Certain extremophile microorganisms — halophilic bacteria and archaea — do manage to survive, and during periods of heavy rainfall that briefly reduce surface salinity, blooms of red algae have been documented, turning patches of the sea a striking reddish-pink. Life, as it always seems to find a way, has carved out even this hostile niche.

A Landscape Under Threat

The Dead Sea is shrinking. Over the past several decades, the diversion of water from the Jordan River for agricultural and municipal use has dramatically reduced the inflow to the basin. The water level drops by more than a meter per year, and sinkholes have opened along the shoreline as fresh underground water dissolves the underground salt deposits left behind by retreating brine. The iconic shoreline resorts and floating platforms that gave the Dead Sea its tourist allure have had to relocate repeatedly as the water line recedes.

Various projects have been proposed over the years to stabilize the sea, including a proposed canal from the Red Sea, but political complexity in the region has prevented any large-scale intervention. What future generations experience at the Dead Sea may be a very different landscape from the one that made it famous.

The Experience of Floating

For the millions of tourists who visit each year, the practical reality of the Dead Sea is as peculiar as the science promises. Entering the water is fine; staying upright is difficult because the buoyancy forces your body into an involuntary recline. Most visitors end up reading newspapers and posing for the classic floating photograph, arms and legs in the air. Getting the water in your eyes or mouth is intensely painful due to the mineral concentration. And emerging from the water leaves a visible residue of salt on the skin — a tangible reminder that you have just floated in one of the most chemically extreme bodies of water on the planet.

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FactOTD Editorial Team

Published March 28, 2026 · 4 min read

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