Following a recent collision, you observe a new buoy near the reported position of the sunk vessel. The buoy shows: blue and yellow vertical stripes; pillar shape; topmark of a standing figure (upright cross); light alternating blue and yellow flashing. What is this and what action do you take?

A. EMERGENCY WRECK MARKING BUOY (EWMB). Introduced by IALA in 2012 to rapidly mark newly discovered or recently sunk wrecks before a chart update can be issued. Colour: BLUE and YELLOW vertical stripes (unique — not to be confused with safe water red/white vertical stripes). Topmark: an upright yellow cross (standing cross shape). Light: alternating BLUE and YELLOW flashes — the only buoy in the IALA system showing BLUE light. This blue/yellow alternating light is unique to EWMBs and should be immediately recognisable at night as marking a new hazard. Action: treat as an UNCHARTED DANGER — pass well clear on all sides; the wreck beneath may have uncertain extent; report the buoy position to authorities to confirm chart data; do NOT rely on the chart for depth information around this mark; maximum vigilance.

B. Blue and yellow stripes indicate a pilot vessel at anchor. The alternating blue/yellow light is the pilot boat recognition light used in some port approaches.

C. This is a new style of preferred channel mark. Blue/yellow alternating means neither channel is clearly primary — navigate with caution and contact port authority.

D. An EWMB marks a wreck that has already been surveyed and cleared. The blue light confirms the wreck is no longer a hazard — normal navigation can resume around the mark.

A. IALA System A — Red to PORT when entering harbour (proceeding from seaward). Red can buoy on your port side means you are on the starboard side of the channel, heading seaward (leaving harbour). To re-enter, you would keep the red buoy to PORT. Rule: In IALA A: RED = PORT = entering harbour (coming from sea). Green = Starboard = entering harbour. Memory aid for IALA A: "Red to Port Returning." The question states the red buoy is to port — therefore you are ENTERING HARBOUR correctly, keeping the channel to starboard. Pass the red buoy keeping it to PORT (leave it on your port side). In IALA B (Americas, Japan, Philippines, Korea): colours are reversed — red to starboard entering.

B. In IALA A, red buoys are always on the starboard side of the channel. Pass the red buoy keeping it to starboard — it marks the starboard side of safe water.

C. IALA A and B are interchangeable in UK waters. The MCA has adopted a combined system since 2015 where red marks starboard in all UK harbour approaches.

D. Red can buoys are cardinal marks indicating danger to the north. Pass to the north of the buoy regardless of the direction of travel.

A. NORTH CARDINAL MARK. Topmark: two cones BOTH pointing UP (like an arrow pointing north). Colour: black over yellow (black upper, yellow lower). Light: white VQ (very quick) or Q (quick) — uninterrupted. Meaning: safe water lies to the NORTH of this mark. The mark indicates a hazard to its south — the safe side to pass is to the NORTH. Action: pass the mark to the NORTH — i.e., keep the mark to the SOUTH of you as you pass. In this scenario the buoy is bearing 358° (nearly north), so you are approaching from the south — the mark is warning you of danger to your south; you are already in the safe water north of the mark. Monitor: do not pass to the south of this buoy.

B. North cardinal marks are passed to the east. The topmarks and colour confirm this is a north cardinal but the passing convention is to leave it to port when heading north.

C. Two cones pointing up indicate an isolated danger mark. Pass on either side with caution as the danger is directly beneath the buoy.

D. VQ white light with black/yellow topmark indicates a special mark. These do not indicate hazards and may be passed on any side.