IALA buoyage · Lateral marks
Starboard-hand lateral mark
Differs by region — showing A
Marks the starboard (right) edge of the channel when travelling with the direction of buoyage — a green cone in Region A, a red cone (nun) in Region B.
Fl G 4sOne flash every 4 s — dark longer than light. Colour: green.One flash every 4 s — dark longer than light. Colour: green.
Conical buoy; solid colour: green; topmark: one cone, point up. Light: Fl G 4s.
What it means
The starboard-side limit of the navigable channel, taken in the direction of buoyage. The pointed cone (nun) shape means “starboard side” in both regions; only the colour flips.
What you do
Going with the direction of buoyage (e.g. entering harbour), leave this mark on your starboard side. Leaving harbour, keep it to port.
Memory aid
The cone points up like a mountain you steer right around. Region B (the Americas): “red right returning” — red nun on your right when returning from sea.
Region A vs Region B
Same mark, same meaning, same shape — only the colours flip. Select a region to preview it site-wide.
Source: IALA Maritime Buoyage System — USCG Navigation Center, U.S. Aids to Navigation System