What action should be taken when a fog bank is observed ahead?

When a fog bank is observed ahead, the appropriate action is to put the engines on stand-by and reduce to a safe speed. This course of action aligns with the principles of navigational safety, particularly in restricted visibility situations such as fog. Reducing speed allows for better reaction times to unexpected developments, such as encountering other vessels, navigational hazards, or changes in the environment. It also minimizes the risk of collisions, which is paramount when visibility is limited.

Navigating at a safe speed ensures that the vessel can be effectively maneuvered and that there is sufficient time to take necessary action if the situation changes, such as the appearance of other vessels or obstacles. Additionally, it is part of good seamanship to remain vigilant and prepared in potentially hazardous conditions, adhering to the COLREGs that emphasize the importance of safe navigation practices.

In this context, maintaining normal speed or engaging engines at full speed would be inappropriate as these actions could lead to dangerous situations without sufficient visibility to assess and respond to them properly. Similarly, relying on the autopilot without addressing changes to speed and readiness for manual control would not be advisable; effective seamanship requires active engagement and situational awareness, particularly in reduced visibility conditions.