What are vessels that have an alternately flashing red and yellow light engaged in?

Vessels displaying an alternately flashing red and yellow light are engaged in public safety activities. This combination of lights is specifically used to indicate that a vessel is conducting operations that serve the public, such as search and rescue missions, law enforcement, or other similar emergencies. The use of distinct light signals helps to communicate the vessel's status to other mariners and ensure safety on the waterways.

In contrast, while vessels engaged in commercial fishing or recreational boating may have specific lighting requirements, they do not utilize the flashing red and yellow light pattern that denotes public safety operations. Ambulance services, which typically do not operate on water, are also not relevant in this context. Thus, the correct answer reflects the purpose and function of the light signal.