Module 5 - COLREGs
Day Shapes
What you will learn
Recognise the complete day-shape pattern, distinguish compulsory from optional signals, and connect shape to observed operation and collision duties.
Day shapes communicate status or activity, but meaning comes from the exact arrangement and observed operation—not one familiar silhouette.
A vessel at anchor displays a ball. A vessel proceeding under sail while also propelled by machinery displays a cone, apex downward, forward where best seen. NUC displays two balls vertically; RAM displays ball-diamond-ball. A vessel aground displays three balls vertically where Rule 30(d) requires them; that paragraph refers back to the anchor lights, not to an additional anchor ball.
A vessel engaged in fishing displays two cones with their apexes together. If outlying fishing gear extends more than 150m horizontally, it displays an additional single cone, apex upwards, in the direction of the gear. The ordinary fishing shape does not depend on that extended-gear condition.
For a tow exceeding 200 metres, the towing vessel and towed vessel or object display a diamond where prescribed. A power-driven vessel constrained by her draught may exhibit a cylinder. 'May exhibit' matters: the cylinder and corresponding three red lights are optional, and the underlying status depends on draught in relation to available navigable water. No shape creates absolute right of way.
The cone classifies the yacht as power-driven while machinery propels it, even if sails remain set.
| Shape | Meaning | Boundary |
|---|---|---|
| Ball | At anchor | Read with position and anchor-watch evidence |
| Cone apex down | Sail plus propelling machinery | Treat as power-driven |
| Two balls | Not under command | Exceptional inability to manoeuvre |
| Ball-diamond-ball | Restricted in ability to manoeuvre | Restriction arises from the nature of work |
| Two cones apex together | Engaged in fishing | Gear must restrict manoeuvrability |
| Cylinder | Constrained by draught | A qualifying vessel may exhibit it |
Interpret shape plus operation
A vessel shows two cones apex together and an additional cone apex up to starboard while gear is visible there.
1. Identify base status
Two cones apex together identify a vessel engaged in fishing.
2. Locate extended gear
The additional cone points towards gear extending more than 150m.
3. Create sea room
Assess collision risk and avoid vessel and gear while applying channel or overtaking duties.
Sense check: The additional cone does not replace the two-cone fishing shape; it adds gear direction and extent.
Common mistake or limitation
- The constrained-by-draught cylinder is optional under Rule 28; it is not mandatory for every qualifying vessel.
- Two cones apex together identify fishing generally; the additional apex-up cone marks gear extending more than 150m.
Recap
- Read the full arrangement and connect it to observed operation.
- Fishing uses two cones apex together, with an additional cone towards gear extending more than 150m.
- A constrained-by-draught vessel may exhibit a cylinder; no shape creates absolute right of way.
Optional quick check
Section 11 of 12
What does an additional single cone, apex upwards, shown with fishing shapes indicate?
Sources and factual review
Reviewed 2 September 2026 - Coastal Skipper Revision.
Continue studying COLREGs
This public lesson is part of Revision Module 5. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.