What does the term 'freeboard' measure on a ship?

The term 'freeboard' specifically measures the distance from the waterline to the main deck of a ship. This measurement is crucial for understanding a vessel's safety and stability, as it indicates how much of the ship's hull is above the waterline, which can help prevent water from boarding the ship during rough seas. A higher freeboard generally suggests better sea-keeping characteristics and reduced risk of flooding in adverse conditions. Hence, in naval architecture and ship design, freeboard is an essential factor in ensuring a ship can operate safely in various maritime environments.