Which type of draft mark is used to determine displacement?

• A. Calculative
• B. Limiting
• C. Navigational
• D. Plimsoll

Answer: (A)

Displacement is the ship’s weight, which you infer from how much water the hull displaces. To get that, you need the draft—the vertical distance from the keel to the waterline. Different draft marks on the hull have different purposes. Plimsoll marks (load lines) show the maximum safe draft under various conditions and are about safety limits, not weighing the ship. Navigational draft marks help with depth checks for safe passage, not with calculating weight. Limiting marks indicate upper bounds for draft, again related to safety rather than measurement of displacement. The calculative draft marks are the ones used when determining displacement because they provide standardized reference points for performing weight and trim calculations using the measured draft and the water’s density.