BOTH INTERNATIONAL & INLAND While underway in fog, you hear a vessel ahead sound two prolonged blasts on the whistle. Which action should you take?

Correct Answer: Option B — Sound only fog signals until the other vessel is sighted

Rule 35(b) states that a power-driven vessel making way through the water shall sound at intervals of not more than two minutes one prolonged blast. Two prolonged blasts are not a standard fog signal for a vessel underway; therefore, you must continue sounding your own fog signals until visual contact occurs.