>>945433YOU CANNOT BUY "JUST BUY PASSAGE" ON A CARGO SHIP.
Are you the guy from /trv/?
I challenge you, just walk up to a ship and ask them how much it would cost to carry you somewhere.
Once you realize ports are secure areas, and they won't let you in, then you might begin to grasp what you're saying.
Yes, you can go to a website and book a cruise on specific cargo ships, but there is a lot going on behind the scenes, and it's a complex process, not something you're going to do same-day.
Ships clear customs each time they stop in a new country. The ship will provide a crew list to the agent before the ship ever arrives, so they know who's coming. If a crewmember is departing the ship in a particular port, they'll be taken by the ship’s agent to immigration, where they'll be stamped into the country.
Mariners typically are given shore passes or some sort of special permission to leave the port by the host gevernment. This may come with a restriction to stay within a certain radius of the port. This is a very special thing just for mariners.