A passenger ship must be designed and loaded so that it can remain stable when it turns or encounters changing conditions. Stability depends on the vessel’s shape, the distribution of its weight, the amount of cargo it carries, and the position of that cargo. Ballast water—water deliberately carried in designated tanks—also plays an important role in helping a ship maintain the required stability.
The Sewol had been modified after being brought into service in South Korea. The alterations increased its upper structure and affected its stability. Investigators found that the vessel departed with substantially less ballast water than required while carrying excessive cargo. The cargo was also inadequately secured. These conditions reduced the ferry’s ability to remain upright when it made a sharp turn.
To understand why these factors mattered, imagine a tall object balanced on a narrow base. If its weight is concentrated high above the base, even a relatively small movement can make it unstable. A ship works differently in detail, but the underlying principle is similar: the distribution of weight affects how readily the vessel can return to an upright position after leaning.
