What should a mariner never rely on when plotting a voyage?

A mariner should never rely solely on a floating buoy being on station as charted when plotting a voyage because buoys can drift due to various environmental factors such as currents, tides, and wind, or may be out of position due to maintenance or accidental displacement. While charted positions of buoys provide valuable references, their physical locations must be confirmed visually or with other navigational tools. This ensures the accuracy of navigation and helps avoid potential hazards.

In contrast, fixed navigational landmarks offer stable points of reference that are unlikely to change position. Compass readings, while they can be affected by magnetic variations, are essential for navigation and should be used carefully alongside other tools. Radar information is also crucial for detecting obstacles and other vessels, particularly in low visibility conditions, thus contributing to safe navigation. Every navigational aid is important, but an overreliance on buoys without verification can lead to dangerous situations.