What term describes the lines around the weatherdecks to prevent personnel from falling overboard?

The term that describes the lines around the weatherdecks to prevent personnel from falling overboard is "Lifeline." Lifelines are essential safety features on a ship, designed specifically to provide protection by creating a barrier that personnel can hold onto, thus reducing the risk of accidental falls into the water. They are often made from strong, durable materials and are secured at various points along the weatherdeck.

In a maritime context, while the other options, such as guard rails and safety barriers, may provide some forms of safety, they do not specifically refer to the lines intended for preventing falls. Safety lines can refer to ropes used for other safety purposes but are not the standard terminology for the protective lines on decks. Therefore, lifeline is the most accurate term that encompasses the function and specific design of these safety features on naval vessels.