Maybe the benefit would be there if you could move with a ton of luggage wthout being overcharged for it?
https://www.lowtechmagazine.com/2008/06/ocean-liners.html
> to transport one passenger across the Atlantic, a plane needs 4 times more engine power than a ship. Energy output does not say all there is to say about fuel consumption however, since it does not take into account the duration of the trip (see comments) and the fuel efficiency of the engines. It says even less about the emissions of toxic fumes and CO2, because marine engines burn much dirtier fuel than aeroplanes.
> If we would stuff people in the Queen Mary 2 like we fold passengers in airplane seats, the ship could transport more than 500,000 people ... [This] would boil down to a power output of 0.18 kilowatts per passenger – comparable to the output of a well-trained cyclist and 700 times more efficient than the engine power per passenger of an airplane. Taking into account the duration of the voyages, the ship scores 70 times better than the plane.
> Transporting 30,000 people on the QM2 is far from unrealistic or uncomfortable ... Every one of those 30,000 passengers on the Queen Mary 2 would have 20 times as much space than a passenger on a plane, while at the same time consuming 43 times less engine power (taking the view that both engines has similar efficiency). Taking into account the duration of the trip, the ship is 4 times more energy efficient than the plane.Now this looks like an option that could be useful in a peak oil world.
> Replacing planes by ocean liners would be an ecologically sound idea, but only if marine engines become cleaner. Most ships make use of very dirty (unrefined) diesel oil that needlessly poisons the air and heats up the atmosphere. This is not a technological but a political problem.
I'd found a 57% sale on cabins right after Christmas 2018, and even with upgrading to have an ocean facing balcony, that room for the three of us was 25% cheaper than three transatlantic airline tickets, including our flight to Southampton and from NYC to our final destination.
We were moving, so being able to bring as much luggage as we could handle also mean no extra baggage charges. Cunard has slowed their crossings to 7 nights at sea, since most passengers cross for the experience.
The ship's Internet connection was more expensive and slower than I thought the price was worth, so I didn't bother. It was super nice to have time for reflection on my previous work assignment before arriving and starting the next---and all with no jetlag.
I spent some time working offline on a personal python project in one of the lounges. Also read a book on creativity and another about the changing international monetary order from the ship's library---said to be the largest library on the open oceans. One of the people lecturing in their auditorium/planetarium was a former chief counsel for the NSA (though I can't recall his name), lecturing on surveillance; fascinating Q&A with the audience afterwards (Asked what he fears most when kicking back with friends around a campfire, he said he fears the dissolution of nation-states).
Other passengers with cruise line experience said that the QM2 is different---their kids program and entertainment options are minimal compared to cruise ships, but then again, the QM2 is built to cross the north Atlantic comfortably, and her cruising speed, or 2/3s of maximum speed, matched the top speeds of most cruise ships. Cunard requires formal dress in all but one restaurant and in public spaces on the ship after 18:00 each evening, alternating formal and black-tie, with tuxes available to rent. My wife, my son, and I had a blast dressing up and 'going out in the town' in the middle of the North Atlantic.
So, if you watch for a good sale, it can be a very reasonable week of vacation, or an actual transatlantic move.
Cruiseliners aren't exactly low carbon though -- the QE2 had 1900 passengers and managed 125 feet per gallon at normal cruising speed. That works out 37mpg (us gallons) per passenger
A 777-200 is about 76mpg per passenger.