Why is the initial GM different for vessels carrying different cargo types?

The initial GM, or metacentric height, varies based on the type of cargo a vessel is carrying because different types of cargo have distinct densities and weight distributions, which directly influence how the ship sits in the water. When a vessel is laden with cargo, the weight of the cargo affects the center of gravity (CG) of the ship. Each type of cargo has its own specific gravity, affecting the vertical distance from the waterline to the center of gravity, thus altering the ship's initial GM.

For example, a ship carrying heavy, dense cargo will have a lower center of gravity compared to a ship carrying lighter or more bulkier cargo. This change in the center of gravity leads to a difference in stability, as a lower CG can provide greater stability (higher GM), whereas a higher CG may reduce stability. Therefore, the initial GM is intrinsically linked to the characteristics of the cargo being transported, highlighting why vessels with different cargo types exhibit different initial GMs.