What is the foghorn signal for a power vessel underway?

• A. One Prolonged Blast Every Minute
• B. One Prolonged Blast Every 2 Minutes
• C. Two Prolonged Blasts
• D. Three Short Blasts

Answer: (B)

In fog, vessels use sound signals to communicate what they’re doing so others can adapt. A power-driven vessel that is underway uses a single prolonged blast at intervals not more than two minutes. That long, steady note clearly indicates you’re moving under power, giving nearby mariners a predictable cue about your presence and speed. The cadence is chosen because it’s easy to hear and recognize in poor visibility, helping prevent collisions. Other signal patterns exist for different situations (such as not under command, restricted maneuverability, or being at anchor), which is why the single prolonged blast every two minutes is the correct pattern for a power vessel underway.