Divers discover massive 7,000-year-old underwater wall off the coast of France

Divers have discovered a wall submerged about 7,000 years ago under the sea off western France, scientists said Thursday.

Nearly 400 feet long, it was found off the Isle of Sein in Brittany along with a dozen smaller man-made structures from the same period.

“This is a very interesting discovery that opens new perspectives for underwater archeology and helps us better understand how coastal societies were organized,” Yvan Pailler, professor of archeology at the University of Western Brittany, told News.

He is co-author of a study on the discovery, published in the International Journal of Nautical Archaeology.

The structures were first discovered by retired geologist Yves Fouquet in 2017 on maps of the ocean floor made with a laser system.

The wall is the largest underwater construction ever found in France, BBC News reported.

Divers explored the site between 2022 and 2024 and confirmed the presence of granite structures.

“Archaeologists did not expect to find such well-preserved structures in such a harsh environment,” Fouquet said.

They date from between 5,800 and 5,300 BC, are located nine meters under water and were built at a time when sea level was much lower than today.

Researchers believe they may have been fish traps built on the beach or walls to protect against rising sea levels.

The study states that the structures reflect “technical capabilities and social organization sufficient to extract, move and erect blocks weighing several tons, similar in mass to many Breton megaliths”, large stone ensembles used as monuments or for ceremonial purposes.

This technical knowledge would be several centuries prior to the first megalithic constructions.

The study’s authors speculate that the site may be at the origin of local Breton legends about sunken cities, according to BBC News. One of those lost cities, Ys, was believed to be located in Douarnenez Bay, just a few kilometers to the east.

“It is likely that the abandonment of a developed territory by a highly structured society has become deeply rooted in people’s memories,” the study states. “The submergence caused by rapid sea level rise, followed by the abandonment of fishing structures, protection works and habitable places, must have left a lasting impression.”

The discovery comes about six months after archaeologists found the remains of a 16th-century merchant ship. over 1.5 miles underwater off southern France, the deepest find of its kind in the region.