When there is sufficient sea room, what is the most effective action to avoid a collision?

Altering course alone is the most effective action to avoid a collision when there is sufficient sea room, as it allows the vessel to move in a predictable manner that is clear to other navigators and ensures safety without creating additional complications. By changing course, the vessel can create a safe passage away from potential collisions while maintaining its navigation and speed.

This action aligns with navigational practices that prioritize clear communication with other vessels and maintaining a safe navigation path. It helps in establishing an immediate and effective response to a developing situation and is in line with the general principles of safe navigation as per the COLREGs.

Other choices, while potentially useful in certain contexts, do not provide the same level of clarity and proactive maneuvering as altering the course does. For example, changing speed significantly could lead to confusion regarding the vessel’s intentions and may not effectively resolve a close-quarters situation, especially if the other vessel does not anticipate such a change. Sounding the horn mainly serves as a warning rather than an evasive action. Dropping anchor might be an emergency measure but is not practical for collision avoidance when sufficient room is available. Thus, altering the course alone is a direct and effective technique for collision avoidance in open waters.