What signal indicates that a vessel is operating astern propulsion?

• A. Three short blasts
• B. One long blast
• C. Two short blasts
• D. Four long blasts

Answer: (A)

In this topic, you’re learning how vessels use whistle signals to show what they’re doing. Three short blasts specifically tell other vessels that the engine is being put into astern propulsion, meaning the propeller is in reverse. That reversal can change how quickly the vessel slows, stops, or changes direction, and it can create a different wake, so nearby boats should take care and give extra room or adjust their own actions accordingly. The other sound patterns are for different maneuvers or communications and don’t indicate reversing propulsion, so they wouldn’t be the correct interpretation in this situation.