In fog, a power-driven vessel underway but stopped and making no way must sound which signal?

• A. Two prolonged blasts at not more than two-minute intervals
• B. One prolonged blast every two minutes
• C. Two short blasts every minute
• D. One short blast every minute

Answer: (A)

In restricted visibility, vessels use whistle signals to communicate their status and intended actions. For a power-driven vessel that is underway but not making way, the signal is two prolonged blasts, repeated at intervals not exceeding two minutes. This pattern clearly indicates you are present but stationary, so other vessels know to take appropriate action to avoid a collision. The two-long-blasts instruction also provides a regular cadence so the signal isn’t misinterpreted in fog.

Other signal patterns would convey different information about maneuvering or movement and would not accurately describe a vessel that is not making way, so they wouldn’t be appropriate for this situation.