This doesn’t make sense to me. It has more to do with the individual than the sector.
Otherwise it seem like what is being said is the ultimate mariner would be a person who takes a boat out, (no tugs!), makes monkey fists, takes celestial fixes, weaves mats out of rope and does donuts with the boat (no bow thruster!) but has no skills that would make the vessel useful.
There are a lot of skills needed to run a ship that are not specific to going to sea. I have to do payroll, work budgets and so forth A yacht captain has to deal with what ever he has to deal with. Same as any working mariner.