Ok, you're closer now, and they have taken no action. What action should you take to indicate doubt that they will avoid collision?

• A. Five or more short and rapid blasts on the whistle.
• B. Inform the Master.
• C. Do nothing.
• D. Increase engine speed.

Answer: (A)

When you are close and the other vessel hasn’t acted, you use a distinct whistle signal to show you doubt they will keep clear. Five or more short, rapid blasts on your whistle is the recognized cue that you’re uncertain they’ll avoid collision, and it should prompt them to take or confirm action. This audible warning communicates your doubt to the other vessel and helps prevent misunderstanding.

Informing the Master is an internal action, not an audible signal to the other vessel. Doing nothing provides no warning, and increasing engine speed is a personal maneuver rather than a signal to others. The five-short-blast signal directly serves the purpose of indicating doubt and prompting the other vessel to respond.