Which of the following best describes a vessel "underway"?

A vessel is considered "underway" when it is not at anchor and is not made fast to the shore. This definition is crucial because it indicates that the vessel is able to navigate through the water, regardless of whether it is moving or stationary in the water. The term encompasses vessels that are actively traveling as well as those that may be drifted due to currents or winds but are still capable of maneuvering.

In contrast, if a vessel is anchored or aground, it implies that it is secured to the sea floor or remains in a fixed position, and thus cannot be classified as underway. A vessel docked at the marina is also not underway, as it is tied up and secure at a berth. While a vessel moving freely without restrictions suggests that it is underway, the core defining characteristic is solely whether the vessel is at anchor or secured to land, hence making the third option the most accurate description.