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?

Originally, in 2014, Laurent Ballesta had just one precise objective: to unravel the mystery of groupers. To understand the issues involved in their collective reproduction. But although focused on the study of groupers, the real surprise came from the sharks. Never before had the team been confronted with such a density of grey reef sharks. The divers took up the challenge of counting them. Methodically, they repeated the operation many times to arrive at the impressive figure of 700 grey reef sharks. Each year, the team returned to the southern pass of Fakarava in French Polynesia. Until 2019, for the fourth expedition, "Gombessa 4" is the synthesis of precise and unique scientific protocols. The mission demonstrated that shark hunts are not anarchic, but rely in part on social organization within the horde, following in the footsteps of the 700 grey sharks in "700 sharks in the night (Gombessa 4, Genesis)".