What distinguishes being “underway” from being “aground”?

The term “underway” refers to a vessel that is not anchored, aground, or attached to the shore. This definition is crucial for understanding navigation and the responsibilities of vessels at sea. Being underway implies that the vessel is capable of movement and is free to maneuver, which is essential in avoiding collisions and adhering to navigation rules.

This differentiates “underway” from being “aground,” where a vessel is resting on the bottom or stuck in shallow water, therefore unable to move freely. Being attached to a buoy, in the process of moving, or being docked at a marina does not encompass the full context of the term “underway,” as these scenarios may involve a vessel that is not necessarily free to navigate. The distinction outlined in the correct answer provides a clear understanding of the operational status of the vessel concerning its duties and navigation rules under the COLREGs.