Cap Corse, the mystery of the rings
Off the coast of Cape Corsica, strange rings dot the seabed. How did they appear? The story of a multidisciplinary scientific investigation coupled with an extraordinary underwater expedition, led by diver and naturalist Laurent Ballesta.
This curious phenomenon was observed in 2011 on a sonar screen during an oceanographic survey in the Cap Corse and Agriate Marine Natural Park. About twenty kilometers off the coast of the Isle of Beauty, on a vast sandy plain, at a depth of more than 100 meters, 1,417 regular circular shapes appear over nearly 15 km². These almost perfect rings, 20 meters in diameter, appear to have been drawn on the seabed. These unusual geometric patterns have aroused the curiosity of the scientific community. A long-planned expedition will attempt to uncover their secret. It is led by Laurent Ballesta, a diver, photographer, naturalist, and extreme diving specialist, who is surrounded by a multidisciplinary team of some forty researchers—biologists, geologists, ecologists, and paleoclimatologists. To achieve this, he is utilizing technology already tested during Planète Méditerranée: a pressurized bathyal station that allows four divers to explore the great depths without time limits, while living confined for twenty-one days in a 5 m² cabin. This feat was made possible thanks to the logistical support of the French Navy, which provided a military vessel to ensure their safety. Using this underwater station, an observation submarine, and numerous scientific protocols, the team, from analysis to hypothesis, is gradually unraveling the mystery of the origin of these strange rings and the exceptional biodiversity they harbor.
This documentary retraces three years of a scientific investigation full of twists and turns. After the initial reconnaissance dives uncovered a surprising underwater landscape, major discoveries, pleasant surprises, and disappointments followed. As fascinating for specialists as for the uninitiated, the investigation’s findings reveal a unique ecosystem. Against all expectations, these strange rings provide us with information about the Earth’s last ice age. Throughout the dives, Laurent Ballesta’s photographs reveal a profusion of species, some photographed for the first time, reminding us of the extent of our ignorance of the sea closest to us, the Mediterranean.
92 min. Available on ARTE.TV until 02/08/2027. Broadcast on ARTE on Saturday, May 3, 2025, at 8:55 PM.
