Could the Future Hold Alternative Fuel Cruise Ships?

It seems like today everyone knows someone who drives a hybrid car and talk of the next big thing is right around the corner for the automotive industry. So my question is whether or not an alternative fuel cruise ship would work? Cars get miles to the gallon but cruise ship fuel usage is in gallons per minute. Even when not in motion, the amount of fuel required to keep all the electricity flowing on board would give a hybrid car owner a heart attack. Again, back to my question, could it work? Would hydrogen be a possibility for a ship? Hydrogen production either uses water or creates water which is not a problem for a ship. But the logistics and safety makes that a difficult sell. The ships are already hybrids so to speak with the diesel electric generators on board dedicated to making sure you can run the hair dryers and watch TV in your state rooms. The next thing to question is bio diesel. With the amount of food that is prepared on a cruise ship, this has got to be the way to go! Besides it has been said that vehicles running on spent vegetable oil tend to smell like french fries and that would not be a problem on deck with the grills going anyway. In all seriousness, the cruise line have come a long way in becoming as environmentally friendly and efficient as they can with what they have to work with but there is always going to be the question of what next.