Cargo ships that offer passenger accommodation are usually container ships or general cargo ships. Cargo ships often travel between locations that are not often considered tourist destinations. Travel by cargo ship is generally possible year-round.
Cargo ships usually only have a few cabins on board, so passengers need to be book them about six months in advance. Only about a dozen passengers are allowed on board each trip. The duration of each stop is approximately 12 hours, but differs depending on the cargo, so it is always wise to check in advance. Accommodations aboard a cargo ship are decent, as each cabin usually has its own bathroom, and passengers dine with the captain and his officers.