I imagine a bunch of drones zig-zagging around your ship in the middle of the night are much less predictable and harder to hit than if they are coming at you fast but in a straight line. You are bound to lose track of one of them in the chaos. There's also less of a risk that the drones blow each other up when one gets inevitably hit. Plus, there's probably a significant delay in the controls on top of the difficulty of steering an unstable watercraft like this.