Which part of a ship can be measured from the waterline up to the weatherdeck?

The term that refers to the distance between the waterline and the weatherdeck is known as freeboard. Freeboard is an important safety measurement that indicates how high a ship's deck is above the water, which can be vital in evaluating a vessel's seaworthiness and overall stability. A higher freeboard can enhance a ship's ability to handle waves and prevent water from entering, contributing to its safety in adverse conditions. The measurement is specifically concerned with the vertical distance from the water's surface to the deck level, making it a critical aspect of naval architecture and ship design.

In contrast, the other terms refer to different ship components. The mast is the tall structure that supports sails or other equipment, the main deck is the upper deck of the ship where much of the operational activities take place, and the propeller is the mechanical component used to propel the vessel through the water. None of these directly conveys the meaning of the vertical measurement from the waterline to the weatherdeck, distinguishing freeboard as the correct answer.