Co-funded by France’s military navy, the Pourquoi Pas? undertakes hydrographic surveys and other missions to scan the water column and map the sea floor. She can deploy two heavy submersibles simultaneously, and collect samples by coring or dredging. The research vessel Pourquoi Pas? operates in a number of disciplines: (1) Deep-sea and coastal hydrography with the deployment of hydrographic launches; (2) Scanning the water column and currents; (3) Mapping the sea floor by means of echo sounders and profiling the substrate (seismology, gravimetry, magnetism); (4) Multiscale studies of physical, biological and geological processes; (5) Site reconnaissance using echo sounders, either by deploying towed, remotely controlled and autonomous submersibles (SAR, Victor 6000 and Nautile respectively) or by lowering heavy tethered devices (Penfeld) into position close to the sea floor; (6) Collecting and analysing samples of water, living material, sediment and rock; (7) Deploying assistance to submersibles experiencing difficulty, such as the French navy’s Newtsuit.