🔍 Key Concepts

• Dredging and underwater operations day shapes in the Navigation Rules • Difference between safe side and obstruction side signals on a dredge • Meaning of two black balls in a vertical line vs other shapes like diamonds or ball‑diamond‑ball

💭 Think About

• Think about what a dredge needs to communicate to other vessels about where it is safe or unsafe to pass. • Ask yourself: when a vessel is restricted in its ability to maneuver because of dredging, how does it mark the side where there is an obstruction? • Compare the shapes shown on the port side with the shapes that would indicate the side on which other vessels should pass.

✅ Before You Answer

• Verify in the Navigation Rules what two black balls in a vertical line specifically indicate for a dredge or vessel engaged in underwater operations. • Check which side (safe or obstructed) is marked by balls and which is marked by diamonds. • Confirm that the shapes shown are day shapes for the nature of the work or hazard, not just general status like moored or not under command.