Polymer electrolyte fuel cells (PEFCs) for air-independent propulsion systems have been developed and tested under submarine conditions and are thus ready for submarine application. A demand analysis and the presentation of the requirements for naval surface ships and submarines will be followed by the description of the realisation concepts for PEFC propulsion plants. Based on the results of FC operation on board of a submari2e and the system design for the new German submarine Class 212, synergy effects will be derived from that for surface ships. Finally, future aspects will be pointed out including PEFC propulsion for merchant ships.