IALA buoyage · Cardinal marks
South cardinal mark
Identical in A and B
Yellow over black with both cones pointing down: safe water lies to the south — pass south of it. White light Q(6)+LFl 15s.
Q(6)+LFl 15s6 quick flashes followed by one long flash every 15 s.6 quick flashes followed by one long flash every 15 s.
Pillar buoy; horizontal bands top to bottom: yellow, black; topmark: two black cones, points down. Light: Q(6)+LFl 15s.
What it means
Danger lies to the north of this mark; the safe, navigable water is on its south side. Identical in both IALA regions.
What you do
Pass to the south of the mark.
Memory aid
Both cones point down = south (bottom of the compass), at the black band below. Light: 6 flashes = 6 o’clock, plus one long flash so you can’t miscount it as 9 or 3.
Source: IALA Maritime Buoyage System — USCG Navigation Center, U.S. Aids to Navigation System