What does 'underway' mean in nautical terms?

In nautical terms, 'underway' refers specifically to a vessel that is not at anchor, nor is it aground. This definition is crucial because it describes the vessel's status in terms of its movement and operational capacity. When a vessel is considered underway, it means that it is capable of navigation, whether moving through the water or prepared to do so. This is a fundamental concept in maritime regulations, as it affects the application of various rules, including those concerning navigational lights, sound signals, and the obligations of vessels in different scenarios.

The other contexts, such as being anchored, moored, or in distress, do not align with the definition of underway, as each of these conditions indicates that the vessel is not actively navigating but rather stationary or experiencing an emergency situation. Understanding this distinction is essential for proper navigation and compliance with the Collision Regulations (COLREGs).