My parents traveled on container ships quite a few times (twice to NZ and OZ). Trips are typically booked through specialised travel agents (you can find them quite easily via Google). There is quite a community of people doing these trips, mainly pensioners, because you need to have time and can't be sure about timing.
For those thinking about doing it, the Asia/Africa routes from Europe are much more interesting. Going across the Atlantic or Pacific is much less interesting. Also in the modern age of container freight you don't have much time at the ports, and often the captains are reluctant to let you get off, because they are on such tight schedule and delays would quickly cost 100s of 1000s of dollars per hour (that will give you an idea about the economic impact of this blockage).
My mother actually travelled on a loose cargo freighter in the 90s. That was a completely different experience because you would often have several days or a week at port.
For those thinking about doing it, the Asia/Africa routes from Europe are much more interesting. Going across the Atlantic or Pacific is much less interesting. Also in the modern age of container freight you don't have much time at the ports, and often the captains are reluctant to let you get off, because they are on such tight schedule and delays would quickly cost 100s of 1000s of dollars per hour (that will give you an idea about the economic impact of this blockage).
My mother actually travelled on a loose cargo freighter in the 90s. That was a completely different experience because you would often have several days or a week at port.