The shipping industry is becoming increasingly visible on the global environmental agenda. Shipping's share of emissions to air is regarded to be significant and public concern lead to ongoing political pressure to reduce shipping emissions. International legislation at the IMO governing the reduction of SOx and NOx emissions from shipping is being enforced, and both the European Union and the USA are planning to introduce additional regional laws to reduce emissions. Therefore new approaches for more environmental friendly and energy efficient energy converter are under discussion. One possible solution will be the use of fuel cell systems for auxiliary power or main propulsion. The presentation summarizes the legal background in international shipping related to the use for gas as ship fuel and fuel cells. The focus of the presentation will be on the safety principles for the use of gas as fuel and fuel cells on board of ships and boats. The examples given show the successful integration of such systems on board of ships. Furthermore a short outlook will be given to the ongoing and planed projects for the use of fuel cells on board of ships.