What is the definition of a vessel's center of gravity (CG)?

The definition of a vessel's center of gravity (CG) is fundamentally tied to the concept of weight distribution within the vessel. The center of gravity is the point at which the total weight of the vessel is considered to act vertically downwards, focusing solely on the gravitational effects on the vessel's structure.

This point is crucial for understanding the stability of the vessel because it serves as a reference for determining how the weight of the ship is distributed above the waterline. Knowing the location of the center of gravity helps in calculating the righting arm and stability of the vessel during various loading conditions, ensuring that it remains safe and upright in the water.

While the buoyant force and how weight is distributed are important concepts in vessel stability, they refer to different aspects. The buoyant force is associated with the center of buoyancy and how it interacts with gravity, rather than the center of gravity itself. Similarly, while trim refers to the fore-and-aft balance of the vessel, it does not define the center of gravity but rather describes how the position of the center of gravity influences the vessel's trim. Thus, the correct choice clearly encapsulates the essential definition of the center of gravity in the context of maritime stability.