Off the coast of Cap Corse, strange rings dot the seabed. How did they come to be there? The documentary ‘Cap Corse: The Mystery of the Rings’, directed by Yann Rineau, recounts a multidisciplinary scientific investigation combined with an extraordinary underwater expedition, led by the diver and naturalist Laurent Ballesta in collaboration with scientists, including Professor Edouard Bard, holder of the Chair in Climate and Ocean Evolution at the Collège de France, and his team, who took part in this adventure both in their CEREGE laboratory and in the field or underwater in a sub off the coast of Cap Corse.
It was a curious phenomenon observed in 2011 on a sonar screen during an oceanographic survey in the Cap Corse and Agriate Marine Nature Reserve. Some twenty kilometres off the coast of the ‘Isle of Beauty’, on a vast sandy plain at a depth of over 100 metres, 1,417 regular circular shapes are visible across an area of nearly 15 km². Almost perfect rings, 20 metres in diameter, which appear to have been drawn on the seabed. These unusual geometric patterns have piqued the curiosity of the scientific community.
A large-scale expedition, long in the making, is set to attempt to unravel their mystery. It is led by Laurent Ballesta, a diver, photographer, naturalist and specialist in extreme diving, who is supported by a multidisciplinary team of researchers, including Edouard Bard and his colleagues at CEREGE, who are responsible for developing numerous scientific protocols.
For the dives, the expedition is deploying observation submersibles and a pressurised bathyal station, which allows divers to explore the deep sea without any time constraints, whilst living in confinement for around twenty days in a cabin measuring just a few square metres. This feat has been made possible thanks to logistical support from the French Navy, which is providing a military vessel to ensure their safety.
This documentary film chronicles three years of a scientific investigation full of twists and turns which, following the initial reconnaissance dives that revealed a surprising underwater landscape, led to a succession of major discoveries, pleasant surprises and setbacks. Against all expectations, these strange rings provide insights into the Earth’s most recent ice age. Through a process of analysis and hypothesis-testing, the investigations gradually unravel the mystery of the origin of these strange rings and their unique ecosystem, highlighting the extent of our ignorance regarding the sea closest to us: the Mediterranean.
The film ‘Cap Corse: The Mystery of the Rings’, directed by Yann Rineau, will be broadcast on the ARTE channel on Saturday 3 May at 8.55 pm, and will then be available on arte.tv from 26 April 2025 to 2 August 2027. A film written by Yann Rineau, Laurent Ballesta and Aurine Crémieu – a co-production by ARTE France, Les Gens Bien Productions and Andromède Océanologie.
