A Plimsoll Mark, also known as a load line, waterline or simply Plimsoll line, is a vital safety marking found on the hull of a ship that shows the maximum depth to which a ship may be safely loaded. There are several synonyms for Plimsoll Mark, including load line, water level, registration mark and draft mark. These markings are important in ensuring the safety of both the vessel and its crew, as overloading can cause serious accidents and instability. The Plimsoll Mark is a legal requirement for all ships and vessels, and failure to comply with its standards can result in penalties or even legal action.