IALA buoyage · Emergency wreck
Emergency wreck-marking buoy
Identical in A and B
Blue-and-yellow vertical stripes with an upright yellow cross, light alternating blue/yellow: a new wreck not yet on your chart.
Al Bu/Y 3sAlternates blue → yellow every 3 s.Alternates blue → yellow every 3 s.
Pillar buoy; vertical stripes: blue and yellow; topmark: an upright yellow cross. Light: Al Bu/Y 3s.
What it means
Marks a new, recently discovered wreck that has not yet been promulgated in charts and notices to mariners. It is placed as close as possible to, or above, the wreck and is usually temporary. Identical in both IALA regions.
What you do
Give it a wide berth and slow down — the wreck may extend well beyond the buoy, and its exact position may still be uncertain.
Memory aid
Blue and yellow = brand new. Nothing else afloat shows an alternating blue/yellow light — one second blue, one second yellow.
Source: IALA Maritime Buoyage System — USCG Navigation Center, U.S. Aids to Navigation System