What does a vessel displaying yellow over yellow lights indicate?

The display of yellow over yellow lights indicates that a vessel is engaged in an overtaking situation, typically as per the navigation rules. In maritime practice, vessels display specific lights to communicate their status and intentions to other vessels. When a vessel shows two yellow lights, one above the other, it signals that it is not only preparing to overtake but is also potentially limited in its ability to maneuver while doing so. This is crucial for other vessels to understand, as it helps to avoid collisions by clarifying the actions of the overtaking vessel.

In this context, the other options represent different situations that do not involve the specific lighting configuration of yellow over yellow. For example, fishing operations would generally use different lighting signals to indicate their activity. Similarly, a grounded vessel or one that is anchored would again use distinctive light signals that differ from the yellow over yellow configuration. By understanding what yellow over yellow lights mean, mariners can maintain safe navigation practices and avoid misunderstandings on the water.