Has air travel totally replaced such a travel option? Why?
Not everyone is in so much of a hurry that a week or so of travel by sea is not an option, and that could reduce emissions. Or is it that the economics do not work out?
Given that there appear to be no "sea route" travel options for passengers remaining, the answer would appear to be: yes.
> Why?
Most likely, speed. Second most likely: cost.
> Not everyone is in so much of a hurry that a week or so of travel by sea is not an option, and that could reduce emissions.
But, also, not enough people are willing to take a week of sea travel to get from point A to point B to provide enough volume for the ships. People spent a week at sea in 1900 not because they wanted to spend a week at sea but because there was no other faster option for that travel.
Speaking as an American, most people here don't have the luxury of taking a week off for a leisurely cruise to a destination.
I'm also not sure just how much a ship sailing across the ocean or a sea compares to an airplane traveling the same distance. I wouldn't be surprised if they were comparable.