What does a two-ball day shape indicate during daylight?

• A. Not under command
• B. Not under control
• C. In good visibility
• D. A fishing vessel

Answer: (A)

A two-ball day shape signals that the vessel is not under command. This means the vessel cannot maneuver as required by the collision regulations, usually due to a failure or restriction (like engine or steering problems). Because it cannot reliably keep to a safe course or speed, other vessels must take early and substantial action to avoid it and pass at a safe distance. The two balls are displayed vertically during daylight to communicate this status; at night, the equivalent signal is two all-round red lights in a vertical line.