What does "freeboard" measure on a vessel?

Freeboard refers to the vertical distance between the waterline and the upper deck of a vessel. It is essential for assessing a ship's stability and safety at sea, as it indicates how much of the vessel is above the waterline. A greater freeboard generally enhances the ship's ability to handle rough waters by reducing the amount of water that can wash over the deck during waves.

Measuring freeboard is crucial during vessel design and operation to ensure that there is adequate reserve buoyancy and to meet regulatory standards for different types of vessels. This measurement helps in determining how much water could potentially be on the deck before the risk of flooding occurs.

The other options focus on different aspects of a vessel's design and operational characteristics, but they do not accurately describe what freeboard specifically measures. For instance, the depth from the waterline to the bottom of the hull pertains to the draft of the vessel, the area above the waterline is a broader term that doesn't capture the specific measurement of freeboard, and the level of cargo storage relates to weight and space, which is not synonymous with freeboard.