What is defined as the height of a vessel's hull from the waterline to the main deck?

The term that represents the height of a vessel's hull from the waterline to the main deck is known as freeboard. Freeboard is an essential measurement used to assess the safety and stability of a vessel. It provides information about how much of the vessel is above the waterline, helping to determine its ability to handle waves and potential flooding. A higher freeboard indicates that more of the vessel is above water, which generally means it’s less likely to take on water in rough conditions.

In the context of vessel design and operation, maintaining an adequate freeboard is crucial for ensuring that the vessel can navigate safely in various sea conditions. It is a key consideration in stability calculations, especially for boats that operate in rough or changing weather.

In contrast, draft refers to the vertical distance between the waterline and the bottom of the hull (keel), representing how deep the vessel sits in the water. Displacement is the volume of water a vessel displaces when floating and is generally related to the vessel's weight. Free depth, while not a commonly used term related to hull measurement, can refer to the vertical clearance within a hull but does not apply to the measurement from the waterline to the main deck.