Which vessels are not allowed to show yellow lights under the International Rules?

• A. Sailing vessels underway
• B. U.S. submarines
• C. Vessels not under command
• D. Vessels engaged in fishing

Answer: (B)

Under the International Rules, a yellow light is a special signal used to indicate a vessel engaged in fishing (a specific operation with its own lighting pattern). Submarines, being naval vessels, are not assigned a yellow signaling option and would not use yellow lights as part of their standard navigation lights. When surfaced, they follow the normal navigation lights (red, green, white) and, when submerged, navigation lights don’t apply in the same way. So, the class that is not permitted to display yellow lights under the rules is U.S. submarines, because yellow is reserved for specific civilian operations like fishing and is not used for naval signaling.