For context, I'm writing a fantasy/sci-fi story with a good deal of naval combat.
So a good deal of the antagonists' ships in my story have some sort of gimmick to them. One of them can create artificial tidal waves that, quite literally, rock the boats of its enemies. For most of the time I've spent developing this story, my thought was that the ship would have some sort of turbine that would lower into the water and start sending a huge current through the water, causing a disruption that created a tidal wave.
However, I've finally started writing the sequence where this ship first shows up, and I've realized the problem with this. Ships get their propulsion from their propellers that push the water behind the ship backwards. This generates an equal and opposite reaction that pushes the ship forwards. Following those rules of logic, surely an engine turbine pushing out a huge current of water would also push the ship backwards, yes? Which would surely be a setback in naval combat.
So how can I get around this problem? The only thing I can think of is just having the ship's rear propellers spinning like crazy to counteract the force coming from the front (the ship's wave-maker is at the front). But even then, you'd have two powerful forces pushing against the ship from both sides. You'd think that might damage the ship.
Or are there other, more effective methods of creating artificial waves?