What is the recommended caution level for a vessel constrained by her draught?

A vessel constrained by her draught is one that cannot safely navigate in shallow water or when the water depth is insufficient for her submerged portion. The characteristics of such a vessel mean that it may have limited maneuverability and may be more susceptible to grounding or other navigational hazards.

Therefore, it is important to exercise full caution in these situations. This involves being aware of the specific conditions that could affect the safe passage of the vessel, such as water depth, tide changes, and nearby obstructions. Consequently, the recommended course of action is to maintain full vigilance and adapt movements appropriately to ensure safety when navigating through areas where the draught may become a limiting factor.

In contrast, the other options minimize the risks or suggest a lack of diligence that could endanger the vessel's safety and complicate navigational situations, especially in potentially hazardous waterways.