1st to 28 July 2019


Science, technique and underwater adventure

The photographer, biologist and expedition leader Laurent Ballesta and his 3 companions, Antonin Guilbert, Thibault Rauby and Yanick Gentil, set themselves an unprecedented challenge: remaining 28 days in a row at a pressure 13 times that of the surface, equivalent to an average depth of 120 metres. The challenge: considerably extending the diving time to better explore unknown deep-sea ecosystems, which are usually poorly accessible to divers and over a very short time. The sporting challenge, ecological stakes and unique images, make this expedition a new milestone in the history of scuba diving.

What did I come here to do? Explore the sea? I already know everything that can be seen there. I have descended in the pursuit of a mirage, I have succumbed to the vertigo of this blue tear and I have reached the very centre of the dream.



The Monaco Explorations and the Prince Albert of Monaco Foundation supported this expedition with many facets, whether scientific, physiological, or promises of pictures revealing an unknown marine life. Laurent Ballesta and his partners collaborated with more than ten scientific teams. In the sites explored between Marseilles and Monaco, several types of experiments and sampling have been carried out according to precise protocols followed by the divers: seabed mapping, search for rare species, study of pollution levels, water sampling to study environmental DNA, sampling of gorgonians, etc.


Combination of the two techniques

Saturation diving (confinement in a space kept under pressure) and  recreational deep diving  (use of scuba rebreathers) give divers the freedom to explore previously undiscovered spaces for hours. Laurent, Antonin, Thibault and Yannick remained in a pressurised steel bathyal station (at the pressure of the depths explored, between 7 and 13 bars).

400 hours of diving

The 4 divers came out each day using a diving bell under which they recovered their scuba rebreathers once on-site, and then set out for a one- to three-hour exploration dive. Only limit in time: the resistance to cold. They performed 31 dives, i.e. more than 400 hours of diving between 60 and 144m in 28 days.

Briefing before the dive © M.Boussion EDM​

Diving bell ©Laurent Ballesta, Andromède Océanologie, GOMBESSA 5


Benthic bell jar ©Laurent Ballesta, Andromède Océanologie, GOMBESSA 5

Benthic bell jar ©Laurent Ballesta, Andromède Océanologie, GOMBESSA 5

Benthic bell jar ©Laurent Ballesta, Andromède Océanologie, GOMBESSA 5


Carbon sinks

The mesophotic area, an intermediate zone between 60 and 180 metres deep located between surface light and total darkness of the abyss, remains largely to be discovered. The explorers of Gombessa 5 describe a variety of ecosystems, characterised by a high density of sponges, invertebrates, and the presence of large quantities of calcareous algae. Benthic bell jars were installed on these organisms at various depths to directly measure photosynthetic activity and respiration. The aim: to know whether these ecosystems sequester carbon dioxide or whether, on the contrary, they release CO2.

The analysis of the measurements performed is underway and will take several months.

Four divers... and thirty or so crewmen

Laurent Ballesta is a photographer, biologist and leader of underwater expeditions. He has already directed four other Gombessa expeditions.

Antonin Guilbert is a marine biologist and professional diver. He has taken part in many mapping campaigns to monitor the quality and management of the marine environment.

Thibault Rauby is a dive instructor and lighting assistant. A reference in terms of ‘diving tech’, he has worked on various projects, including all the documentaries about the Gombessa Expeditions.

Yannick Gentil is a diver and underwater camera operator. He is the dedicated cameraman of the Gombessa expeditions. 

Photograph of the Gombessa 5 team as the divers are coming out of the chamber on 28 July 2019©Didier Théron

Sampling of gorgonians

During the mission, Laurent and his team cooperated with the Monaco Scientific Center (CSM) to carry out a work on five gorgonian species, among which the red coral. Samples were collected during several dives and brought to the surface team present on the catamaran that followed the barge throughout the mission. These samples are currently being processed at the SCM for ecophysiology and genetic analyses.

Red coral Corallium rubrum ©M.Boussion

Gorgonian off Monaco ©Laurent Ballesta_Andromede_Gombessa V


Callanthias ruber ©Laurent Ballesta, Andromède Océanologie, GOMBESSA 5

Loading of the diving bell before the dive ©M.Boussion Explorations de Monaco


Precious photographs

The great freedom of movement and the prolonged diving time facilitated the taking of exceptional pictures, ranging from completely untouched natural sceneries to rarely observed animals living in their environment, such as this Callanthias ruber. Those species and many others have never been photographed before. All these pictures will be the subject of a photographic exhibition in 2020.

A validated tool for environmental DNA ​

Already tested during previous missions of Monaco Explorations, environmental DNA is a very promising technique to study the ‘genetic’ traces left in the sea water by marine animals during their passage at a given time, in a given place. The DNA traces are recovered after filtering (in a sterile environment) the seawater, pumped at the desired depth. These traces are then compared to known genetic maps. During the mission, the divers of Gombessa 5 optimised a new sampling technique developed by Spygen, a biotechnology company which uses a continuous filtration pump system, fixed to the diver or to any other support. This enabled the filtration of 30 litres of water on a 500 m route and the method has been validated. A promising technique for environmental DNA.


Sites explored 1 Gombessa 5 ©L.Ballesta, Andromède Océanologie

Sites explored 2 Gombessa 5 ©L.Ballesta, Andromède Océanologie

Sites explored 3 Gombessa 5 ©L.Ballesta, Andromède Océanologie

Sites explored 4 Gombessa 5 ©L.Ballesta, Andromède Océanologie