Special marks indicate a special area or feature referred to in nautical publications. They are not primarily intended to assist navigation.
- Colour: yellow
- Topmark: single yellow X-shape (St. Andrew's cross)
- Light: yellow, any rhythm not used for other marks
- Shape: optional — any shape not conflicting with lateral or safe water marks
Examples include: ocean data acquisition systems (ODAS), traffic separation marks, spoil ground marks, military exercise zone marks, cable or pipeline marks, recreation zone marks.
An interactive 3D illustration is shown here. The same content is described in the rule text and key takeaways below.
Buoyage Reading Order
Read the mark in a fixed order: topmark, colour pattern, light rhythm, charted meaning, then the safe side or action required.
Confirm the conventional direction of buoyage from the chart or pilotage plan before deciding port-hand or starboard-hand treatment.
Treat every mark as one aid among several.
Cross-check with charted depth, position, radar, visual bearings and the planned track.
Exam Focus
For cardinals, use the cones first, then the colour bands, then the flash mnemonic.
If those three agree, the answer is usually secure.
For lateral marks, the region only changes the colours, not the core idea: the mark still identifies the side of the channel in the conventional direction of buoyage.
Key Takeaways
All yellow colour scheme
X-shaped (cross) topmark in yellow
Yellow light distinguishes from navigation marks
Indicates special areas — check nautical publications for details
Common Mistakes
Assuming special marks indicate a navigational hazard
Not consulting charts/publications for what the mark indicates
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