I'm developing a game set in a colossal landmass at the center of a vortex, with water walls dozens of kilometers high. The continent is somewhat circular, and no civilization has yet developed seafaring technology that can survive the vortex itself.
During the game, different civilizations go to war, and one of them develops a plan to take by surprise the capital of another by riding the vortex to get "behind" the defending forces.
Is there a design that could help a ship survive fairly reliably the extremely strong but otherwise fairly regular currents? Keep in mind that the water is spiraling up, not down.
I have a few ideas about how to solve the "water direction" problem (ballast, or a ship hull that forces the ship to go down, so that the upward thrust of the water is balanced), but otherwise I really am...out of my depth!
EDIT: a few more informations, based on the comments.
- The vortex is an annulus (a ring), but I can't think of any way in which the inhabitants could test wheter or not this is true.
- The continent is a disc, it's flat.
- The total landmass is about 100 million square kilometers, 50 million less than earth's own landmass. It's pretty much a smaller pangea.
- The vortex needs an incredible amount of energy to be sustained, and the movement of the water walls create very, very strong winds near the coast. This prevented pretty much any kind of development in seafaring technology, because it's considered madness to "challenge" the vortex. It's why the idea of exploiting its motion to attack another city is crazy enough that it might work. But it needs a ship with some form of ballast (be it physical or simply a design peculiarity that makes the ship tend to go down instead of following the current, that spirals up), and a design that accounts for the immense amount of energy in the elements surrounding the ship.
Basically, the ship needs to be strong enough not to be torn apart by wind & water.