🔍 Key Concepts

• narrow channels hydrodynamics (bank suction, squat, interaction between vessels) • effects on a vessel’s handling and control when another vessel passes very close astern or alongside • how water flow and pressure change between two hulls moving in the same direction in confined water

💭 Think About

• Picture two ships in a narrow channel, one overtaking the other. As the overtaking ship closes on the stern and comes very close, what happens to the water between the two hulls? Does it speed up or slow down, and what does that do to pressure? • Think about whether low pressure between two close‑moving hulls will tend to pull them together or push them apart. • Consider whether getting very close to another vessel in a narrow channel usually makes control and separation easier or more difficult.

✅ Before You Answer

• Be clear this is about hydrodynamic interaction, not Rules of the Road sound signals or lights. • Focus on what happens as you approach the stern closely, not far away or after you have fully passed and opened distance. • Verify in your mind whether close‑quarters interaction in restricted waters is generally considered a risk of vessels being drawn together or being forced apart.