Final answer:
The safety lanyard on a vessel, or engine shut-off switch, is designed to automatically cut off the boat's engine if the operator is thrown overboard or moves away from the controls, enhancing overall boating safety.
Step-by-step explanation:
The purpose of the safety lanyard (engine shut off switch) on a vessel is to provide an essential safety feature that immediately stops the engine if the operator falls overboard or is not in a position to control the vessel.
This is similar to knowing where specific safety equipment is located in a laboratory, such as the fire extinguisher and the eyewash station.
The safety lanyard is typically a cord that attaches the operator to the switch; if the operator moves too far away from the helm due to an abrupt situation, such as falling overboard, the lanyard is pulled and the engine shuts off to prevent further incidents or injuries.