Which light configuration indicates that a vessel is aground?

A vessel that is aground is required to display two all-round red lights. This configuration clearly signals to other mariners that the vessel is in a situation that may restrict its ability to maneuver. The use of red lights is universally understood as a warning signal, indicating danger or a hazardous condition. This is particularly vital in conditions of limited visibility or where other vessels might be present, as it alerts them to exercise caution and provide ample distance.

The other light configurations do not convey that a vessel is aground. For example, green and white lights do not carry specific meaning in the context of being aground and are used for other purposes, such as indicating a sailing vessel underway or its position. Similarly, a single white light would not serve as an appropriate signal for a vessel in distress or aground, as it typically represents a different situation altogether. Blue lights are used to indicate specific types of operations and are not part of the standard COLREGs identification for vessels aground.