Two prolonged blasts at not more than two-minute intervals is the fog signal for which situation?

• A. Power-driven vessel underway in fog but stopped and making no way
• B. Sailing vessel underway in fog
• C. Vessel not under command in fog
• D. Vessel at anchor in fog

Answer: (A)

In restricted visibility, sound signals let other vessels quickly understand what your vessel is doing. Two prolonged blasts, spaced not more than two minutes apart, indicate a power-driven vessel that is underway but not making way. That means the engine is on, you’ve not stopped due to anchoring, but you’re not moving forward—perhaps because the propulsion is failing or you’re temporarily halted. Other vessels should treat you as a stationary power-driven vessel and pass with caution, giving you extra room since you could drift or restart propulsion unexpectedly. This tone is different from the signal for a vessel at anchor (one prolonged blast) and from signals for other statuses, which use different patterns.