When navigating at night, what does yellow over white signify?

When navigating at night, the combination of yellow over white lights indicates that a vessel is towing another vessel astern. This configuration is part of the navigation lights regulations, which are designed to ensure safe passage and help identify the actions and status of different vessels on the water.

The yellow light at the top signifies that the towing vessel is engaged in towing operations, while the white light below indicates a stern arrangement. This helps other vessels recognize that there is a tow involved, which is critical for maintaining safe distances and navigating effectively in various marine conditions.

In contrast to the correct answer, the other options convey different situations. For example, a single white light typically signifies a vessel at anchor, while other arrangements would indicate different activities like fishing or working with a fellow vessel. Understanding these light configurations is crucial for night navigation and helps prevent collisions and ensures the safety of all vessels on the water.