What is the primary function of mooring lines?

Mooring lines are essential for securing a ship to fixed structures such as wharfs, piers, or even to other ships, providing stability and preventing movement while at dock. Their primary role is to ensure that the vessel remains in a designated position, effectively counteracting the forces of wind, current, and wave action that might otherwise cause the ship to drift away from its intended location. By using mooring lines, crews can safely prepare the ship for loading, unloading, and conducting onboard operations without the risk of misalignment or collision with other structures or vessels.

The other options relate to functions that are not directly associated with mooring lines. Controlling a ship's speed pertains more to propulsion and maneuvering systems, anchoring involves the use of an anchor and chain to hold a ship in deep water, and protecting the hull typically involves fenders or other protective measures, not mooring lines themselves.