What should a vessel do in dense fog if it does not have operational radar?

In the event of dense fog where a vessel does not have operational radar, anchoring could be a prudent choice if it can be done safely. This action allows the vessel to remain stationary rather than navigating in potentially hazardous conditions where visibility is severely limited. By anchoring, the vessel reduces the risk of collisions with other vessels, as well as running aground or becoming disoriented in the fog.

This approach aligns with the principles of COLREGs, which emphasize the importance of ensuring safety at sea and taking necessary actions to prevent collisions. When visibility is poor and navigation becomes difficult without radar, anchoring provides a temporary respite and allows the crew to assess the situation before proceeding.

Other options may present risks: continuing on course could lead to collisions with unseen obstacles or other vessels; signaling for assistance may not be effective without knowing the proximity of other vessels; and simply reducing speed does not eliminate the dangers posed by the surrounding environment. Therefore, anchoring is the safest and most responsible action in this scenario, should conditions allow for it.