What dayshape would a vessel aground show during daylight?

• A. One black ball
• B. Three black balls in a vertical line
• C. Three white balls
• D. Two black balls

Answer: (B)

Vessels use day shapes to communicate their current status to others in daylight. When a vessel is aground, it cannot maneuver and needs to signal this restricted ability clearly. The signal for that situation is three black balls displayed in a vertical line, so other mariners understand the vessel is stuck on the ground and may be unable to keep clear or maneuver.

A single black ball indicates the vessel is at anchor, not aground. Two black balls in a vertical line signals not under command, which is a different restricted condition. Three white balls aren’t a recognized day shape for this scenario. So three black balls in a vertical line best represents a vessel that is aground.