Ships typically use much lower quality fuels than road going vehicles and don't have much in the way of emission controls. The marine bunker fuels typically used emit 700 times the sulfur dioxide of road-going diesel vehicles. A group of northern European companies is now collaborating on a project to install a fuel cell in a Norwegian offshore oil field supply ship in 2008. The molten carbonate fuel cell stack will use natural gas with on the fly steam reformation to produce the hydrogen to generate the electricity.
The fuel cell ship will be much more efficient than the diesel engines and run much cleaner. Meanwhile Iceland is planning to convert their fishing fleet to hydrogen fuel cells using hydrogen produced by their abundant geothermal energy.