The development of real Autonomous Underwater Vehicles (AUVs) represents a very particular challenge which is being tackled within the scope of the German co-operation project DeepC (www.deepc-auv.de), reaching the middle of the project time frame. The aim of this project is to develop a fully autonomous underwater vehicle for great diving depths, long mission times and a modular design with the following main features: • Mission depth till 4000 m (Crush: 6000 m); • Weight in air 2.4 t; • Cruise speed 4 kts; • Maximum speed 6 kts; • Mission time up to 60 hours; • Operating range up to 400 km; • Payloads ≥ 250 kg. The subjects of vehicle structure, maximum manoeuvrability, electrical power generation, storage and distribution, intelligent behaviour and precise navigation are some of the crucial aspects for the development of such an underwater vehicle. The high speed and manoeuvrability are rendered possible by two horizontal drive systems and four thrusters for transverse and vertical thrust. Electrical motors that are pressure-neutral up to depths of 7000 m are provided for propulsion. A battery-buffered PEM H2/O2 fuel cell whose functionality offers numerous advantages over other systems is used to generate the electrical power needed for DeepC operation. The storage of the reactants hydrogen and oxygen, the trimming-neutral accommodation of the residual water produced, the temperature management and especially also safety problems in connection with the possible development of oxyhydrogen gas are, however, a problem when the AUV is operated independently from an external air supply. Mission management systems perform vehicle guidance, assure intelligent behaviour in special situations, provide a degradation mode for emergencies and/or plan missions independently with due consideration to the targets set. Without external support, the navigation system must allow precise AUV navigation over longer periods of time. Mission-specific sensor systems support vehicle guidance, avoid collisions and perform the actual measuring tasks. Due to a modular payload concept, the vehicle can be easily used for a lot of different missions with a very low amount of mobilisation and demobilisation. The paper describes the current development status in general and the technological highlights like fuel cell, intelligent behaviour, etc. in particular, gives an outlook into the future and shows examples of applications.