Plimsoll lines, also known as load lines or water lines, are reference marks that determine the maximum depth to which a vessel can be safely loaded for a specific voyage. There are several synonyms for this nautical term, including draft marks, load marks, and immersion marks. Another commonly used term is waterline, which refers to the point on the hull where the surface of the water meets the vessel's exterior. The location of the plimsoll line depends on the ship's size, cargo, and intended voyage. It is essential to follow these markings to ensure the vessel's stability and avoid any potential hazards when loading and unloading cargo.