Not saying boats are perfect or that every company that runs them are angels! But you have a lot of head-room if you start off 100x better kg per kg. Because

Not saying boats are perfect or that every company that runs them are angels! But you have a lot of head-room if you start off 100x better kg per kg. Because boats are not perfect doesn't change the original point: A 20% saving on emissions for aircraft and talk of 'having more space for cargo' is missing the big picture - air travel is a massively subsidized luxury where the speed of travel comes at a massive energy cost.