Transatlantic cruises don’t have to be luxurious. If you’re comparing air freight to shipping by sea, it’s very clear ships are far more efficient. We just need to become better at containerising people :)
You mean? Yes.
Yes, you'll need to have a crew and you'll need to need to ship the necessities, which eats into the efficiency of this mode of transport. However, a plane will create 40 times more CO2 for the same amount of cargo transported than a ship. I'd say we can figure out how to fit a larger crew and more supplies in that margin.