"VEHICULES SOUS-MARINS"!

Source ADIT, octobre 2003: Japon, Successful Dive by World's First Fuel Cell Research Submersible
http://www.jamstec.go.jp/jamstec-e/index-e.html
    On August 12, 2003, the Japan Marine Science and Technology Center (JAMSTEC) conducted a successful test of its deep-sea autonomous underwater vehicle (AUV). The "Urashima" is the world's first research submersible powered by a fuel cell. The AUV navigated at depths of up to 300 meters in Suruga Bay while technicians tested the electrical power generating capacity and other functions. JAMSTEC aims to have the AUV make an independent long-distance run of 300 kilometers during fiscal 2004.
    When "Urashima" submerges to its maximum depth of 3,500 meters, the surrounding water pressure reaches 350 atmospheres and the pressure inside the fuel cell reaches about 2 atmospheres. Compared to the operation of fuel cell vehicles (FCVs) under normal atmospheric pressure, under deep-sea conditions the fuel cell cannot easily emit the trace amounts of impurities such as nitrogen and carbon dioxide contained in hydrogen and oxygen gas, as well as the water generated through the process of power generation. Furthermore, if this water is discharged outside the vehicle, neutral buoyancy cannot be maintained.
    "Urashima" therefore employs a "closed system" in which these impurities and water accumulate inside the fuel cell. This system requires more advanced technology than in FCVs under normal atmospheric conditions and represents the world's first practical development of that technology