In fog, which observation would indicate that another vessel is in sight?

• A. You can see it from your bridge
• B. You are receiving AIS data
• C. You hear its engine noise
• D. You see its radar echo only

Answer: (A)

In fog, the only observation that proves you actually have the other vessel in your line of sight is seeing it with your eyes from the bridge. AIS can tell you a vessel’s position, but it doesn’t prove you can see it—the vessel could be out of visual range or obscured. Hearing engine noise might indicate a vessel nearby, but sound doesn’t establish visual contact. A radar echo shows the target on radar, not that you can physically see it. So the direct visual sighting from the bridge is the best indication that the vessel is in sight.