BOTH INTERNATIONAL & INLAND While underway and in sight of another vessel crossing less than .5 mile away, you put your engines full speed astern. Which statement concerning whistle signals is TRUE?

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

COLREGS Rule 34(a) and 33 CFR 83.34(a) require any power-driven vessel operating astern propulsion while in sight of another vessel to sound three short blasts on the whistle, regardless of distance.