Question 1

On an approach to the Thames Estuary you observe a large red vessel with a lantern on a mast and the word "LIGHT VESSEL" on its hull. It shows an all-round white flashing light. Later in the passage you observe a large yellow buoy with a LANBY (Large Automatic Navigating Buoy) designation. How do these differ and how do you navigate with them?

Accepted Answer

LIGHT VESSEL (Lightship): a manned or unmanned vessel maintained in a fixed position to serve as a lighthouse. It is moored by a heavy sinker chain — it does not move from its charted position (within a small swinging circle). Shows an all-round white light characteristic unique to that station (charted). Side identification lights may also be shown. An amber or yellow all-round light may be shown to indicate the lightship is off-station (moved by storm or dragging — a warning that the mark is unreliable). Navigate using the lightship as a fixed navigational reference point; do not pass between the lightship and any associated dangers it marks. LANBY (Large Automatic Navigating Buoy): a large unlit superstructure buoy that replaces a lightship at some stations. Functionally equivalent — it shows a light from a tower on the buoy. Both: check for "off-station" signals. Trinity House maintains both types in UK waters. Lightships and LANBYs are important navigational features on UK coastal passages. Trinity House (the General Lighthouse Authority for England, Wales, and Channel Islands) maintains the lightship and LANBY stations. Off-station signal: if a lightship is off its charted position (storms, emergency maintenance), it shows an amber/yellow all-round light instead of its normal characteristic — this is a critical warning that the navigational reference is unreliable. A vessel that navigates to the position of the off-station lightship and turns based on its position relative to what the chart shows would be using a false reference. Key UK lightship/LANBY stations: Nab Tower, Sandettie LV, Varne LV, East Goodwin LV, Outer Gabbard LV, Sunk Head LV — all on the approaches to the Thames Estuary and Channel. At near-coastal OOW level, the candidate should know the major lightship stations on their trading area and understand that these marks serve the same purpose as a lighthouse — they are charted navigational references, not obstacles to navigate around.

Question 2

You are OOW on a 180 GT coastal supply vessel. At night you observe a small sailing vessel showing only a combined red and green lantern at the bow — no white lights visible anywhere. What is this vessel legally showing and are you required to give way?

Accepted Answer

Combined bow lantern (bicolour lantern) — red (port) and green (starboard) sectors combined in one fitting at the bow — is permitted for sailing vessels under 20m in length under Rule 25(b) and (c): Rule 25(b) permits a combined lantern (red/green/white all in one unit at the masthead); Rule 25(c) permits an all-round white light plus the sidelights. For very small vessels under 7m: Rule 25(d) — if not reasonably practicable to show the prescribed lights, show an electric torch or lighted lantern showing a white light in sufficient time to prevent collision. The vessel showing only the bicolour bow lantern without any white sternlight is technically non-compliant unless it is under 7m using the Rule 25(d) exemption. However: it IS a sailing vessel regardless — you must give way under Rule 18(a)(v). Monitor carefully — the lack of sternlight makes aspect determination difficult. Use radar to determine course and speed. Small sailing vessel lighting arrangements are tested at near-coastal level because coastal waters in the UK contain large numbers of recreational sailing vessels, yachts, and small craft. Rule 25 permits multiple lighting options for sailing vessels, and the variety means the OOW must be able to identify sailing vessel status from whatever lights are shown. Key Rule 25 variants: (a) standard (any size): separate sidelights + sternlight; (b) under 20m: optional combined tricolour at masthead instead; (c) additional option: all-round red over green lights at the top of the mast to be more visible; (d) under 7m or rowing boats: white torch/lantern when in danger of collision. The COLREGs obligation to give way to sailing vessels (Rule 18(a)(v)) applies regardless of whether the sailing vessel is showing its lights perfectly. Non-compliance with light rules by the sailing vessel does not remove the power vessel's give-way obligation — Rule 2(a) requires taking all precautions required by ordinary seamanship.

Question 3

Approaching a harbour entrance, you see (from seaward): a red can buoy to the north of the channel, a green conical buoy to the south of the channel, then a port-hand mark showing Fl.R every 4 seconds. You are heading west (270°) into the harbour. Describe how you navigate through these marks.

Accepted Answer

IALA System A — entering harbour heading west: "Red to Port Returning." (1) Red can buoy to the NORTH of the channel: it is on the port side of the channel (keep it to port) — it marks the northern edge of safe water; your channel track runs to the south of it; (2) Green conical buoy to the SOUTH: it is on the starboard side — keep it to starboard; your channel track runs to the north of it; (3) Fl.R every 4 seconds port lateral mark ahead: red light, any rhythm = port hand mark — keep this to PORT as you pass through the entrance. Navigation: steer a course keeping the red buoy to your port (north of track), green buoy to your starboard (south of track), and the Fl.R to your port as you enter. The area of safe navigation is between the red (port) and green (starboard) lateral marks. Lateral mark navigation is the most practical buoyage skill for coastal and near-coastal OOWs. The key principle: "conventional direction of buoyage" defines port and starboard — in harbour approaches it is from seaward into the harbour. The OOW heading west into a harbour is heading IN the conventional direction (from sea to harbour) — so IALA A port/starboard conventions apply directly: RED = PORT side of safe water (keep to port), GREEN = STARBOARD side (keep to starboard). The phrase "Red to Port Returning" summarises this for IALA A. The Fl.R light characteristic: in IALA A, port lateral marks use RED lights; starboard lateral marks use GREEN lights. Any rhythm of red flashing = port hand mark; any rhythm of green flashing = starboard hand mark. The light rhythm (4 second period in this case) does not change the colour convention — only cardinal marks have specific group-count requirements. At near-coastal OOW level, the examiner expects instant confident application of IALA A conventions in realistic harbour approach scenarios.