On radar you detect a buoy at 358° 0.8nm. As you approach visually you see: two black cones both pointing UP as topmarks; black upper body, yellow lower body; the light characteristic is VQ (very quick flashing — approximately 120 flashes per minute). What is this mark, what does it indicate, and how do you pass it?

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.

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. SOUTH CARDINAL MARK. Topmark: two black cones BOTH pointing DOWN (arrows pointing south, like 6 o'clock on a clock). Colour: yellow over black (yellow upper, black lower — opposite to north cardinal). Light: Q(6)+LFl (6 quick flashes followed by one long flash) white, period 15 seconds. The long flash after the group of 6 is unique to the south cardinal — it helps distinguish it from the east cardinal Q(3) at night. Meaning: safe water lies to the SOUTH of this mark. Action: pass this mark to the SOUTH — the hazard (shoal, wreck, rock) lies to the north of the buoy. Keep the mark to the NORTH of your track as you pass.

B. Two cones pointing down with yellow/black colouring indicate a preferred channel mark. Pass to the south only if you are taking the secondary channel.

C. Q(6)+LFl is the light characteristic for an isolated danger mark. Yellow over black confirms an isolated danger — pass on either side and note the wreck or obstruction beneath the buoy.

D. South cardinal marks are passed to the east. The "south" designation refers to the direction of the main hazard, not the passing side.