🔍 Key Concepts

• Navigation Rules – Part C: Lights and Shapes (Annex I & Rules 20–21) • Meaning of a single green sidelight versus combinations of red/green/white • When an anchor light or masthead light would also be visible at night

💭 Think About

• Ask yourself: From what direction would you see only a single green light on a power-driven or sailing vessel? Think about the vessel’s heading relative to yours. • Consider whether a vessel not making way (anchored or drifting) normally shows a side light alone, or some different light configuration. • Work through each choice and picture, from the Navigation Rules, what lights it should show at night. Which, if any, could present ONLY one green light from your perspective?

✅ Before You Answer

• Verify in the Navigation Rules what lights are required for power-driven vessels underway under 12 meters (small motorboats). • Check the required side lights and stern/masthead lights for a sailing vessel underway. • Confirm what lights a vessel at anchor and a vessel not under command or restricted in ability to maneuver must show, and whether these ever appear as just a single green light from any normal observing angle.