What defines a vessel that is "constrained by her draft"?

A vessel that is defined as "constrained by her draft" refers to a situation where the vessel is unable to navigate safely in shallow waters due to its deep draft. The draft of a vessel is the vertical distance between the waterline and the bottom of the hull (keel). When this draft is significant, it limits the vessel's ability to maneuver in areas with shallow depths.

In practice, vessels that are constrained by their draft cannot operate in regions where the water depth is less than their draft without risking grounding. This definition highlights the importance of water depth in safe navigation and establishes the operational limits of such vessels. It is a critical concept in maritime navigation, particularly for larger ships, which often require deeper water to operate safely.

The other choices do not accurately capture the specific implications of being constrained by draft, as a vessel that can maneuver freely, being transiently anchored, or restricted from departing port does not speak to the limitations imposed by draft depth specifically. Thus, the correct answer aligns directly with the navigational constraints that arise from a vessel's draft.