Which signal indicates a vessel aground during daylight?

Which signal indicates a vessel aground during daylight?

• A. A ball
• B. A square
• C. A triangle
• D. Three black balls in a vertical line

Answer: (D)

In daylight, mariners use day shapes—simple black figures on a white background—to show status. A vessel that has run aground signals this by displaying three black balls in a vertical line. The specific vertical trio is the standardized indicator for grounding, making it clear to nearby vessels that the ship cannot move and needs space. The other shapes don’t indicate grounding: a single ball means the vessel is at anchor, while the square or triangle correspond to different, unrelated signals. The key point is that three black balls stacked vertically uniquely convey that the vessel is aground.

In daylight, mariners use day shapes—simple black figures on a white background—to show status. A vessel that has run aground signals this by displaying three black balls in a vertical line. The specific vertical trio is the standardized indicator for grounding, making it clear to nearby vessels that the ship cannot move and needs space.

The other shapes don’t indicate grounding: a single ball means the vessel is at anchor, while the square or triangle correspond to different, unrelated signals. The key point is that three black balls stacked vertically uniquely convey that the vessel is aground.