capsize

Capsize is the overturning of a watercraft so that it lies on its side or upside down relative to the water surface. It results from a loss of stability and can occur without sinking; a capsized vessel may remain buoyant and afloat on its hull or, in many cases, remain inverted with trapped air. Capsize differs from sinking or foundering, where water fills the hull and the vessel loses buoyancy.

Capsize is caused by a combination of factors that affect a craft’s stability. High winds and large waves, abrupt maneuvers, or sudden weight shifts can overwhelm a vessel’s righting capability. Improper loading, weight distribution, or ballast, as well as design flaws or collisions, can also raise capsize risk. Small boats and lighter craft are generally more prone to capsizing, while larger ships are less susceptible but can still capsize under extreme conditions or structural failure.

From a stability perspective, capsize relates to the center of gravity and the metacenter. If the center of gravity rises too high or the metacentric height is small, the initial righting lever (GZ) becomes insufficient and the vessel can overturn. Some vessels are designed to resist capsizing or to self-right, such as certain lifeboats, but many craft may remain afloat only while inverted.

Prevention focuses on proper loading and ballast, secure equipment, and weather awareness. Wearing personal flotation devices and maintaining safe speeds help reduce risk. If capsized, stay with the vessel if possible, signal for help, and conserve energy; trained crew may attempt to re-right the craft, always prioritizing safety and rescue over self-initiated maneuvers.