Final answer:
The lanyard attached to an ignition safety switch serves to shut off the boat's engine if the operator falls overboard, enhancing safety by preventing the boat from moving uncontrollably.
Step-by-step explanation:
The purpose of a lanyard attached to an ignition safety switch is to shut off the engine if the operator falls overboard. This safety feature is crucial in preventing a runaway boat situation and can potentially save lives by allowing the boat to come to a halt rather than continuing to travel uncontrollably, which can pose a serious hazard to other boats and swimmers. Not only does this function ensure the safety of the person who has fallen overboard by stopping the boat's forward motion, but it also provides an opportunity for them to safely re-board the boat.