160 km southwest of Reunion Island, just a few dozen metres beneath the surface of the Indian Ocean, lies the peak of an underwater volcanic structure known as Mont La Pérouse. The base of this enigmatic geological formation lies 5000 meters below sea level, with a size comparable to that of Mont Blanc. Permanent currents and strong winds characterise this site in the open seas, culminating in complex diving conditions under which Laurent Ballesta, together with his Gombessa diving team and local researchers had to navigate in order to conduct the study in depth. Further techniques such as observation and photographic inventory, biological and geological sampling, and the use of cameras and sonars were employed in this challenging expedition.

The Mediterranean. Because people have been travelling there for thousands of years, it is believed to be without secrets. And yet, far below its surface, lie vast unexplored territories, luxurious gardens worthy of the finest tropical coral reefs. These natural wonders are inaccessible to the traditional diver, in a twilight zone, between 60 and 120 m, where there’s less than 1% of sunlight. If diving at such depths is always a challenge, staying there is a fantasy, a utopia that becomes reality in Planet Mediterranean. In the tradition of Commander Cousteau and his "houses under the sea," the team of diver-photographer Laurent Ballesta is undertaking a new world-record setting mission in complete freedom and without time limit.

Gombessa Expedition 4 Laurent Ballesta went to observe a gathering of thousands of groupers during the full moon of June 2014 (Le mystère mérou) in the southern pass of the Polynesian atoll of Fakarava, where he discovered a pack of over seven hundred grey sharks. How can this unprecedented density be explained? Could it be that social behaviors govern this wild horde? During three years of preparation, he and the other divers on his international scientific team tamed their fear by abandoning the defensive reflexes that provoke shark aggression, with the aim of slipping into the heart of the raging pack to study and film it from the inside. Sharks fitted with microchips, receiving antennas, hydrophones, an ark of 32 synchronized cameras...: a whole technological arsenal is mobilized for the project. As the groupers approach for their annual spawning, what battle plan will the sharks deploy?