What does the term "least depth" refer to in navigation?

The term "least depth" in navigation specifically refers to the shallowest depth of water that has been determined to be safe for a vessel's passage. This concept is crucial for ensuring that a vessel does not run aground, especially in shallow waters where the depth can vary significantly. Navigation charts will often highlight the least depth to guide mariners in maintaining a safe course, avoiding hazards, and ensuring that their vessel has sufficient water clearance.

This definition underscores the importance of understanding local water conditions, as the least depth indicates the minimum required clearance for safe navigation. It is a critical factor in route planning and should be taken into account when assessing the navigability of a particular area.

The other options do not accurately capture the essence of "least depth": the deepest point in a travel route would not ensure safety, as it is not the shallow areas that pose a risk; average depth does not provide the necessary information for safe navigation; and while the minimum depth for any vessel is a concern, it varies from vessel to vessel and does not specifically reflect the local conditions of a navigable area. Therefore, focusing on the shallowest depth pertinent to safe passage directly aligns with the established meaning of "least depth."