Preventive conservation attempts to preserve the integrity of objects. It is a process that begins beneath the surface of the ocean and continues throughout the various stages of the scientific study and treatment of an object.
Based on extensive experience with the shipwrecks at both La Hougue and La Natière, it was decided that the excavation's home base at Saint-Malo should include a structure capable of providing emergency conservation treatment to objects brought to the surface. Starting in 2000, an on-site preventive conservation lab was attached to the excavation site; it was responsible for monitoring objects from their retrieval from the wreck site through the phases of cleaning, storage and conservation. Throughout the life of the project, this method revealed the quality of the connection between archaeologists and the conservators responsible for France's underwater archaeological heritage. It also highlighted the need for close collaboration between the two disciplines. The realities of the terrain showed the various heads of the preventive conservation unit the difficulties of working with an underwater site, but the rigour and painstaking approach of the unit's conservators reminded archaeologists of the extent to which the objects brought to the surface required urgent treatment. The treatment process improved constantly, thanks to constant dialogue between archaeologists and conservators.