Which specific action should the swivel perform in an anchor chain?

The action that the swivel should perform in an anchor chain is to prevent kinking or twisting. Swivels are designed to allow the anchor chain to rotate without causing tangles or kinks. This is particularly important because any twisting of the anchor chain can lead to increased stress on the chain itself and potentially compromise the anchoring system. When an anchor chain kinks or twists, it can hinder the effective deployment and retrieval of the anchor, affecting the stability of the vessel while at anchor. Thus, ensuring that the anchor chain remains straight and free of kinks is vital for maintaining a secure anchorage.