INTERNATIONAL ONLY While underway and in sight of another vessel you put your engines on astern propulsion. Which statement concerning whistle signals is TRUE?

Correct Answer: Option C — You must sound three short blasts on the whistle.

COLREGS Rule 34(a) stipulates that power-driven vessels underway and in sight of another, when operating astern propulsion, shall indicate this by sounding three short blasts on the whistle regardless of meeting or crossing situations.