Which method is effective for improving a vessel's stability?

Ballasting deep tanks is an effective method for improving a vessel's stability. This process involves adding water (or other materials) to the tanks located lower in the vessel, which lowers the center of gravity and increases the overall stability. A lower center of gravity makes it less likely for the vessel to heel excessively in response to external forces, such as waves or wind. Additionally, by increasing the weight lower in the ship, the righting lever (the distance from the center of gravity to the center of buoyancy) is increased, which enhances the stability performance of the vessel.

The other methods mentioned can have different impacts on stability but may not effectively improve it in the same way. For instance, increasing the height of the superstructure typically raises the center of gravity, which can reduce overall stability. Reducing the draft of the vessel can affect stability negatively by reducing the submerged volume and therefore the buoyancy. Enhancing the vessel's hull shape can improve hydrodynamic efficiency, but that does not directly address the stability in the same manner as proper ballasting would.