The deep water exploration (up to 6000 m deep) is a perfect zone for the use of composite materials. The operating conditions (great mechanical stress, long-term immersion) make these materials very attractive. Following several qualification studies, the use of glass/epoxy enclosures for the oceanographic instrumentation protection, up to 6000 m deep underwater, is now widespread. These containers are designed to resist external pressures of more than 60 Mpa. In order to extend the scope of applications of these materials and to meet the demands for specific structures fabrication, several studies have been carried out to assess the possible uses of composite materials for the making of bigger structures such as Autonomous Underwater Vehicles (AUV), used in the seabed study. The opposite figure represents one of the tests carried out by IFREMER on an AUV prototype, ½ scale. The rupture of the cylinder, made thanks to the filament winding process, was buckling-generated under a 600-bar-pressure (6000 m deep).