I believe some cargo ships take a few passengers, I have no idea on costs or time involved, but it might be an adventure.
This thread slipped my attention somehow.
Yes, passengers can be taken on a ship. I had them on large container vessel.
The price at the time was around $ 100 per day. (15 years ago)
Crossing Atlantic is about one week.
However, Pax can stay on board as long as they like, make a round trip, etc.
Deck walks are possible, but should be reported on the bridge. Access to the bridge is allowed, at least when I was on board.
And as an OOW, I enjoyed having pax on the bridge for small talk.
On most of the vessels there is a small swimming pool, bar with TV, laundry, and gym. Swimming pool does not have heated water, water comes from fire line. Warm seas - warm water, and vice versa
Captain can organise a ship tour (and usally does). To see the engine, cargo holds, etc.
Three meals per day. Cabins have bathroom, bed, locker for clothes.
Onboard is a slop chest store for small necessities, like cigarettes, toothpaste, etc.
When time allows, during ocean crossing, most probably there will be a barbique event.
Thats about it.
Ship calls cargo terminals, sometimes miles away from city centers. daily trip to towns can be organised, with a help of captain and the agent. Taxi arranged.
It is rare these days for ship to stay 24 hours in the port. Usually it is between 6 to 12 hours. So local sightseeing has to be planned accordingly.
Generally speaking if not meeting a hurricane or typhoon at high seas, it should be a quiet non-eventful passage, with daily routine, and time to read a book, have a chat with officers and captain, in the evenings