🔍 Key Concepts

• Navigation Rules day shapes for vessels (black shapes shown by day to indicate vessel status) • Rule 30 – Anchored and aground vessels (how many balls are shown and in what pattern) • How towing and underwater operations are shown by day (different combinations of balls, diamonds, and shapes)

💭 Think About

• Look closely at the illustration: how many shapes are there, what kind are they, and how are they arranged? • Ask yourself: which vessel condition in the Rules is the ONLY one that uses three identical black balls in a vertical line by day? • Compare what shapes are required for vessels restricted in ability to maneuver or engaged in underwater operations versus a vessel that cannot move at all.

✅ Before You Answer

• Verify in Rule 30 which condition uses three black balls in a vertical line as a day shape. • Confirm that towing and underwater operations require at least one diamond or a different combination of shapes, not three balls in a row. • Remember that a vessel that is simply drifting (underway, not making way) does not have a special day shape in the Rules.