1 Emily: Also, did you say you were going to Çanakkale? How were you going to get there from Alexandria?
2 Monty: Catch a tramp steamer or something.
3 Emily: So... you do know planes can fly over water?
4 Monty: But flying all the way to Turkey would cost a fortune!
4 Emily: That would be a shame for you, wouldn’t it?

A tramp steamer is a steamship engaged in tramp trade - which is moving cargoes with no fixed schedule or itinerary. Tramp vessels negotiate individual trips on an as-needed basis, picking up cargoes at each successive port as situation demands. They commonly find their next cargo and delivery destination through the use of cargo brokers, although it would be possible for the operators of a tramp vessel to do their own brokerage and find cargoes themselves (much as Serron does for the Space theme characters and their cargo space vessel Legacy^[1]).

Global tramp trade began with shipping in the mid 19th century, and developed into a thriving industry. In modern times, much cargo is shipped in standard containers on ships plying regular trade routes on published schedules, so it's easy to get your product onto a ship going from/to the right places. But there are still tramp ships operating, with the advantage of being available to charter for goods that need shipping to specific destinations on short notice. A few large shipping companies operate as tramp services rather than scheduled delivery routes.

[1] Well, maybe with slightly less ripping people off and doing blatantly criminal deals.