If you’re a landlubber like me, you have little to no idea how long it takes a ship to sail from one place to another. That will change by the end of this chapter, but we have considerable leeway in deciding the length of any journey. Much of what follows here is about travel under sail, or by rowing, not by engines. In fantasy worlds, those engines are implausible. In SF, travel is typically through the air. The speed calculations in the section on ship speeds can apply to engine-powered ships as well, since a knot is a knot and it doesn’t matter what’s causing this speed, with the caveat that winds and oars cannot produce the constant speed of engines.
Several factors influence the difficulty of sailing between locations. The wind direction is chief among them. The ship building skills and seamanship of various countries also impacts this. All of it influences trade routes and which nations can conquer others. A ship would not be able to sail directly into a headwind. Taking an alternative route might force a ship closer to an enemy coastline.
There are several reasons we have leeway in determining the duration of a ship journey:
- Our map, should one exist, is not drawn to scale
- Oarsmen cannot row indefinitely and might have different levels of endurance and training from ship to ship
- Wind speed is not constant even in the open ocean, affecting both the ship itself (if sail powered) and the height of waves that could further impact speed
- Wind direction is also not constant, affecting the angle at which wind fills sails
- Different types of ships sail at different speeds under the same conditions
- Our ship is weighed down by people, cargo, food, and weapons/ammunition, any one of which can change in quantity during a voyage. A ship that just left dock is heavier than one at sea for six months, unless the latter is laden with treasure
- Our ship might be damaged
- Our ship is sailing on a fictitious planet, with possibly a different number of moons and whatever else might affect the seas
Maybe it comes as no surprise that we aren’t sure how long a trip will take. What we’re looking for is a reasonable approximation that a ship will take between X and Z number of hours to travel Y number of miles/kilometers, depending on conditions. But we don’t have to do this. We can just invent numbers and not worry about it. Never stating the distance between two places helps this. Grounding our numbers in some real-world knowledge is an approach that more serious world builders might want to employ, especially if we intend to reuse the setting. Otherwise, we might be inconsistent. Regardless of our choice, the knowledge can help inspire believable details in our work.
For example, let’s say that for our story, we need a trip to take 24 hours, but our calculations reveal that a ship usually takes 24-30 hours. We’re in luck and can do it. When describing that journey, we could state that our sailors enjoyed nearly ideal conditions. This could allow for characters to undertake sword practice on deck or another activity requiring surer footing. A wizard could have time to mix materials needed for spells.
In another scenario, maybe we want our characters to feel confident they’ll make that trip in time. But we want to surprise them and make them arrive late, in 34 hours. We can throw up a storm to slow them, making a character sea sick and preventing others from doing much of anything. Or maybe they battle a ship or sea monster and in so doing lose a mast despite their victory.
We don’t have to do these things, but stories always need unexpected challenges, and if the sea isn’t hard to predict, nothing in our world is.