The correct answer is C) Draining fire-fighting water and pumping it overboard. The key consideration in this scenario is preserving the vessel's stability, which is critical for the safety of the crew and the vessel itself. Removing excess water from fire-fighting efforts is the most important action to maintain the vessel's stability. Accumulated water in the cargo hold can significantly impact the vessel's trim and stability, potentially leading to capsizing or sinking. The other options, while important, are secondary to addressing the water accumulation. Shutting off electricity (A) and removing debris (B) are necessary steps, but do not directly address the stability concerns. Maneuvering the vessel (D) may be beneficial, but should be done after addressing the water accumulation.