The Lakes That Kill: The Red Sea’s Underwater Graveyards

When we think of the Red Sea, the mind usually drifts to biblical mythology—the parting of the waves—or perhaps the vibrant, life-affirming coral reefs that attract millions of tourists to Egypt and Saudi Arabia. But if you were to sink past the recreational divers, past the sunlight zone, and descend nearly a mile into the abyss, you would find something that defies logic: a lake inside the ocean.

These are not merely pockets of water; they are distinct bodies of liquid with their own shorelines, surfaces, and waves, sitting heavily on the seafloor. They are the Red Sea Brine Pools, and they constitute one of the most extreme environments on Earth.

The Ocean’s Toxic Secret

The Red Sea is situated atop a tectonic rift where Africa and Arabia are slowly pulling apart. This geological violence cracks the seabed, allowing seawater to seep deep into the earth’s crust. There, the water dissolves massive deposits of salt and minerals before being superheated and spewed back out.

The result is a brine that is three to eight times saltier than the surrounding ocean. Because of this density, the water does not mix with the sea above it. instead, it pools in depressions on the seafloor, creating a sharply defined interface. If you were piloting a submersible, you would see a distinct “surface” shimmering in the dark. You could create waves on this underwater lake with your thrusters.

The Bizarre Fact: The separation between the ocean water and the brine pool is so distinct that submersibles can literally “bounce” off the surface of the pool due to the drastic change in density.

The Trap of Preservation

These pools, such as the Valdivia Deep or the pools discovered recently by the OceanX mission near NEOM, are devoid of oxygen. They are anoxic death traps. Any fish, eel, or crab that accidentally wanders across the “shoreline” and dips into the brine suffers immediate toxic shock.

However, the horror of the brine pools lies not in the dying, but in what happens afterward. In the normal ocean, a dead fish decomposes. Scavengers eat the flesh; bacteria break down the bones. But inside the Red Sea brine pools, the salinity is so high that bacteria cannot survive. There are no scavengers.

The result is a natural pickling jar. Creatures that swam into these pools decades—or potentially centuries—ago remain perfectly intact, floating in the heavy fluid, preserved in a state of eternal, undisturbed death. It is an underwater museum of perfectly preserved corpses.

The Extremophiles

Despite being lethal to almost all multicellular life, the edges of these pools are scientifically fascinating. They teem with microbial life that thrives on methane and sulfur, offering a glimpse into what life might look like on other planets, such as Jupiter’s moon Europa.

Scientists have observed a grim ecosystem on the “coast” of these underwater lakes. Predators will line up at the edge of the brine, waiting for confused prey to stumble out, intoxicated by the lack of oxygen. It is a hunt that takes place in total darkness, on the shores of a lake that shouldn’t exist.

Research Note: While rare, deep-sea brine pools are found in the Gulf of Mexico and the Mediterranean, but the Red Sea hosts the most extensive and chemically diverse complex of these pools known to science.

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