What is indicated by a vessel displaying an alternating red and yellow light?

A vessel displaying an alternating red and yellow light indicates that it is engaged in public safety activities. This type of signaling is used to alert other vessels and nearby parties that the vessel is involved in operations that may require special attention or caution, such as search and rescue, law enforcement, or other emergency management situations.

This signaling ensures that oncoming vessels understand the vessel's purpose and can take appropriate action, such as yielding right of way or navigating cautiously around the vessel. The use of alternating lights is a widely recognized standard in maritime navigation and enhances safety on the water by clearly communicating the necessity for awareness among other vessels.

In contrast, other colors and configurations are reserved for different types of activities, such as fishing or towing, which each have their own specific light patterns and displays that would not include alternating red and yellow lights.