Chart No. 1 · Q 22
Spherical buoy
Buoys & beacons
A circle glyph is a spherical buoy — the shape of safe-water and some special marks.
What it means
A circle on a position circle is a spherical buoy.
Why it matters
Spheres never mark a side of the channel: the safe-water (fairway) mark is spherical or carries a red sphere topmark, meaning navigable water all around.