At night in a crowded anchorage you observe a vessel displaying: a white all-round light forward (on the bow area) and a white all-round light aft, the forward light appearing higher. The vessel appears to be 200m in length. What does she show and what are your obligations?

A. Two white all-round anchor lights (forward higher than aft) on a vessel over 100m: Rule 30(b) — vessels 100m and upwards in length at anchor shall exhibit a forward all-round white light in the forepart, a second all-round white light in the after part (lower than the forward light), and may illuminate her working decks. She may also illuminate her hull and superstructure in a manner to make her clearly visible (Rule 30(f) — vessels over 100m at anchor shall use available working lights or equivalent). Obligation: vessels under way must keep clear of anchored vessels — anchor lights are warning signals. Plot the anchored vessel's position on radar; give adequate clearance; account for the vessel's swing circle (= cable scope + LOA). By day: one black ball in the forepart.

B. Two white lights at anchor indicate the vessel is NUC — anchored vessels show only one white all-round light, so a second white light means she has suffered a breakdown while anchoring.

C. Only the forward anchor light is required by COLREGs. The second aft light is a company or port authority requirement — it is not a COLREGs signal and can be ignored for collision avoidance purposes.

D. Two white all-round lights mean a pilot vessel at anchor. The forward position of the higher light confirms the pilot is at anchor awaiting duties.

A. Two all-round red lights in a vertical line: this is a VESSEL NOT UNDER COMMAND (NUC) — Rule 27(a). The vessel is unable to manoeuvre as required by COLREGs due to some exceptional circumstance. Obligations: Rule 18 — all power-driven vessels must keep out of the way of a NUC vessel. You are the give-way vessel regardless of aspect or crossing/overtaking geometry. Actions: alter course and/or reduce speed early and substantially to keep clear; do NOT cross ahead of a NUC vessel. Monitor: watch for any green (starboard) or white (sternlight) becoming visible — this confirms aspect and direction of drift; watch for any additional lights (towing, dredging); check for any DSC/MAYDAY on DSC Ch70 or Ch16 — a NUC vessel may be in distress. Rule 35 fog signals for NUC: two prolonged + one short blast every 2 minutes if making way; two prolonged if stopped.

B. Two red vertical lights indicate a vessel constrained by draft. You must keep well clear but can pass ahead if the range is sufficient.

C. Two red lights in a vertical line mean the vessel is at anchor. Anchor lights are all-round white — two reds in a line indicate an anchored vessel with emergency lights on.

D. Two red lights indicates a fishing vessel with gear deployed. Maintain your course and speed as stand-on vessel; the fishing vessel must keep clear.

A. All-round red over white in a vertical line WITH sidelights: this is a PILOT VESSEL underway — Rule 29(a)(i). The red over white is the internationally recognised pilot vessel identification light. The sidelights confirm she is underway and making way. Obligations: no specific Rule 18 obligation to keep clear of pilot vessels — they are treated as power-driven vessels underway for collision avoidance purposes (Rule 18 list does not include pilot vessels). Apply normal Rules 12-17 based on aspect and situation. By day: pilot vessels display the international flag "H" (Hotel — vertical halves, white and red).

B. Red over white all-round lights indicate a trawler — the white is the towing light showing the direction of the gear, and the red indicates a vessel with nets deployed on the port side.

C. Red over white vertical lights indicate a vessel constrained by draught displaying the optional CBD lights under Rule 28.

D. Red over white in a vertical line means a vessel restricted in ability to manoeuvre (RAM). Stand-on rules apply and the pilot vessel should give way to you.