COLREGS Oral Exam Questions and Answers

Rule 1(a): the Rules apply to all vessels upon the high seas and in all waters connected to them navigable by seagoing vessels. But Rule 1(b) lets an appropriate authority make special rules for roadsteads, harbours, rivers, lakes and inland waterways — those local rules take precedence in that area, and must conform as closely as possible to the COLREGs.Lead · local rules win inshore, but only where a competent authority has made them.

No. Rule 1(c) allows a government to make special rules for additional station or signal lights, shapes or whistle signals for warships, vessels in convoy, or fishing fleets — provided, as far as possible, they cannot be mistaken for any light, shape or signal authorised elsewhere in the Rules.Lead · extra signals are permitted so long as they can't be confused with a COLREGs signal.

Rule 2(b) — the general prudential rule. In construing and complying with the Rules, due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from these Rules necessary to avoid immediate danger.Trap · you may depart only to avoid *immediate* danger — not for convenience — and Rule 2(a) still holds you to the ordinary practice of seamen.

No. Rule 2(a) says nothing exonerates any vessel from the consequences of neglect to comply with the Rules or of any neglect of the ordinary practice of seamen or of the special circumstances of the case. A stand-on vessel that holds course into a collision she could have avoided has neglected Rules 17(a)(ii)/17(b) and the practice of seamen.Lead · the Rules never license you to stand on into a collision.

Rule 2(b) — depart from the Rules to the extent necessary to avoid immediate danger. The Rules are a means to avoid collision, not an end in themselves; where obeying the letter of a Rule would cause the very collision it exists to prevent, good seamanship and Rule 2(b) require the departure.Trap · you may depart only to avoid *immediate* danger, and you must be able to justify it — not use 2(b) as a general escape from an inconvenient Rule.

Not under Section II — the Rules always assign one give-way and one stand-on in a crossing/head-on/overtaking case. But in restricted visibility (Rule 19) there is no stand-on vessel — effectively both give way. And under Rule 2/special circumstances a situation not squarely covered may require both to act with the ordinary practice of seamen.Watch · 'both give way' is the fingerprint of Rule 19, not Section II.

Rule 3(g): a vessel which from the nature of her work is restricted in her ability to manoeuvre as required by the Rules and is therefore unable to keep out of the way of another vessel. Examples: laying/servicing a navigation mark, cable or pipeline; dredging, surveying or underwater operations; replenishment or transferring persons/stores under way; launching/recovering aircraft; mine clearance; a towing operation severely restricting the tow's ability to deviate.Trap · a deep-draught ship is NOT RAM — she is a CBD (Rule 3(h)).

NUC (Rule 3(f)): through some exceptional circumstance a vessel is unable to manoeuvre as required and so cannot keep out of the way — e.g. engine or steering failure. RAM (Rule 3(g)): the vessel cannot manoeuvre because of the nature of her work.Lead · NUC is a breakdown she didn't choose; RAM is the job she is doing — same two-red/ball-diamond-ball family of shapes but different day shapes (two balls vs ball-diamond-ball).

Rule 3(k): only when one can be observed visually from the other. It matters because the give-way / stand-on Rules 11–18 apply only when vessels are in sight of one another; if you detect her by radar alone in restricted visibility, Rule 19 governs and there is no stand-on vessel.Trap · a radar contact is not 'in sight' — don't apply the crossing rule to it.

Rule 3(l): any condition in which visibility is restricted by fog, mist, falling snow, heavy rainstorms, sandstorms or any other similar causes.Lead · it's the *cause* reducing visibility, not a fixed range in miles.

Yes. Rule 3(i): 'under way' means not at anchor, not made fast to the shore, and not aground. A vessel stopped and drifting with her engines off is still under way — she is simply not making way through the water.Trap · 'under way' ≠ 'making way'. She shows steaming lights (not anchor lights) and, in fog, the two-prolonged-blast signal for a power-driven vessel under way but stopped.

Yes to both. Rule 3(a): 'vessel' includes every description of watercraft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transport on water.Lead · if it can carry over water, it's a vessel and the Rules bind it.

'Under way' (Rule 3(i)) is a legal state — not anchored, moored or aground. 'Making way' means actually moving through the water under her own power or momentum. A vessel can be under way but not making way (stopped/drifting). The distinction drives the fog signals: one prolonged (making way) vs two prolonged (under way, stopped).Tip · count the prolonged blasts in fog — one = making way, two = under way but stopped.

Rule 4: the Rules in Section I of Part B (Rules 4–10) apply in any condition of visibility — lookout, safe speed, risk of collision, action to avoid collision, narrow channels and traffic separation schemes.Lead · Section I is always on; Section II (11–18) needs vessels in sight, Section III (Rule 19) is for restricted visibility.

Rule 5 demands a proper look-out at all times by sight AND hearing AND by all available means appropriate to prevailing circumstances so as to make a full appraisal of the situation and risk of collision. Radar is 'all available means' — it does not replace sight and hearing.Trap · at night or in reduced visibility a sole OOW may need a dedicated lookout posted; many collisions (and MAIB/DGS findings) turn on a lookout not being posted.

Rule 5 requires a proper lookout at all times; STCW permits the OOW to be sole lookout by day only after a careful appraisal that it is safe, with a lookout able to be summoned instantly. The helmsman on the wheel is not a lookout — his view aft and to the sides is restricted.Trap · at night, restricted visibility, heavy traffic or reduced circumstances, a dedicated lookout must be posted.

Rule 6 — all vessels: state of visibility; traffic density; manoeuvrability (stopping distance and turning ability); background lights at night; state of wind, sea and current and proximity of navigational hazards; draught in relation to available depth. Vessels with operational radar, additionally: characteristics/efficiency/limitations of the radar; constraints of the range scale in use; effect of sea state/weather/interference on detection; that small craft, ice and other objects may not be detected at adequate range; number/location/movement of contacts; the more exact assessment of visibility radar may give.Lead · safe speed is not a fixed number — it's the speed that lets you stop in time within your circumstances.

No. Safe speed is the speed at which you can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions. In open water with good visibility that may be full sea speed.Trap · don't answer 'dead slow' reflexively — the surveyor wants the *appropriate* speed for the conditions.

Yes — a vessel is not entitled to proceed at a speed appropriate only to a working radar picture. Safe speed (Rule 6) is judged on the means actually available; losing radar removes a factor and generally calls for a more cautious speed, especially near hazards or if visibility could reduce.Lead · safe speed follows the means you actually have, not the ones you wish you had.

Rule 7: use all available means appropriate; if in doubt, risk shall be deemed to exist. Use radar properly — long-range scanning, plotting or equivalent systematic observation. Do NOT make assumptions on scanty information, especially scanty radar information. Risk exists if the compass bearing of an approaching vessel does not appreciably change — and may exist even with an appreciable bearing change when approaching a very large vessel, a tow, or at close range.Lead · steady bearing + decreasing range = risk of collision.

Yes — Rule 7(d)(ii): risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.Trap · a changing bearing does NOT guarantee safety with a large ship or a long tow — the far end can still be on a collision course.

No — Rule 7(c) forbids assumptions on scanty information, especially scanty radar information. A single ARPA readout can be wrong (target swap, tracking error, a manoeuvring target). Confirm by systematic observation/plotting and watch the trend.Trap · and Rule 7(d)(ii) — even a good CPA can hide risk when approaching a very large vessel or a long tow, whose far end is on a different track.

Rule 8: action shall be positive, made in ample time and with due regard to good seamanship. Any alteration of course and/or speed should be large enough to be readily apparent to another vessel visually or by radar — a succession of small alterations should be avoided. If there is sufficient sea-room, alteration of course alone may be most effective provided it is made in good time, substantial, and does not result in another close-quarters situation. Check the action's effectiveness until finally past and clear; slacken speed, stop or reverse if necessary.Lead · big, early, obvious — one bold move, then check it works.

Rule 8(f)(i): a vessel required not to impede the passage of another shall, when required, take early action to allow sufficient sea-room for the safe passage of the other. (ii) She is not relieved of that obligation if approaching so as to involve risk of collision and must have full regard to the action required by the Rules. (iii) The vessel whose passage is not to be impeded remains fully obliged to comply with the Rules if risk of collision develops.Trap · 'not to impede' is not a right of way — if risk of collision arises, both are bound by the steering rules.

You may use speed — Rule 8(e) allows slackening, stopping or reversing — but Rule 16 demands action that keeps you *well clear*, and Rule 8(b) wants it large enough to be readily apparent. A speed reduction alone is often not obvious to the other vessel by eye or radar.Tip · a bold course alteration (with sea-room) usually reads more clearly than a speed change; combine them if needed.

The COLREGs give no definition and no fixed width — it is a matter of good seamanship on the local circumstances, judged against the size, draught and traffic of the vessels using it. Working definitions: a narrow channel is a navigable water restricted in width by natural or artificial features so vessels are confined to a limited navigable width; a fairway is the main navigable route through restricted waters.Lead · no width in the Rules — 'narrow' depends on *your* ship; Rule 9 conduct applies to both.

Rule 9(b)/(c): a vessel under 20 metres or a sailing vessel shall not impede the passage of a vessel which can safely navigate only within a narrow channel or fairway; nor shall a vessel engaged in fishing. They may use the channel but must keep out of the way of the vessel constrained to it.Trap · 'shall not impede' — not a prohibition on being there, an obligation not to obstruct.

Rule 9(e): overtaking is allowed only if the vessel to be overtaken has to take action to permit safe passing. The overtaking vessel sounds two prolonged + one short (overtake on your starboard) or two prolonged + two short (on your port) — Rule 34(c)(i). The vessel to be overtaken, if in agreement, sounds prolonged–short–prolonged–short (Morse 'C') and takes steps to permit safe passing; if in doubt she sounds the five short blasts (Rule 34(d)).Lead · ask with the whistle, and don't overtake until she answers 'C'.

Rule 9(g): a vessel shall avoid anchoring in a narrow channel if the circumstances of the case admit.Lead · avoid it if you possibly can; if forced to, keep clear of the fairway and show the correct anchor signals.

No — the COLREGs contain no 'stem-the-tide' rule. Both vessels keep to the starboard outer limit of the channel (Rule 9(a)) and pass port-to-port. A priority for the vessel stemming (or running with) the tide exists only where local by-laws create it (some rivers/ports).Trap · don't quote a stem-the-tide rule as COLREGs — it isn't one.

Rule 9(d) governs: a crossing vessel shall not impede a vessel that can navigate only within the channel — and shall use the doubt signal (five short) if unsure. If you are the channel-bound vessel, the crosser must keep clear regardless of which side she's on. Rule 15 still applies as between two vessels both free to manoeuvre, but Rule 9 prevails for the vessel constrained to the channel.Watch · 'not impede' overrides the ordinary crossing hand-over inside the channel.

Rule 10(c): cross on a heading as nearly as practicable at right angles to the general direction of traffic flow. Join or leave a lane at its termination, or at as small an angle as practicable. Rule 10 does NOT confer right of way — it governs conduct within a scheme; the ordinary steering rules (crossing, overtaking, Rule 18, Rule 19) still apply between vessels.Trap · being 'in the lane' does not make you stand-on over a crossing vessel.

Rule 10: a vessel not crossing, not joining/leaving shall so far as practicable stay clear of the separation line/zone. A vessel under 20 m, a sailing vessel, or a vessel engaged in fishing shall not impede the safe passage of a power-driven vessel following a traffic lane (10(j)). Fishing is permitted in a lane but must not impede. Exempt from the lane-following requirement only when: in danger under Rule 2(b); engaged in laying/servicing a cable; or engaged in an operation for the safety of navigation/RAM within the scheme (10(e)).Lead · small craft, sailing and fishing keep clear of through traffic; only specific safety/cable work is exempt.

You do — Rule 15 (crossing) still applies; Rule 10 governs how you cross but confers no right of way. Crossing 'as nearly as practicable at right angles' does not license you to stand on through a crossing vessel on your starboard side.Trap · being the crossing vessel and being 'in the right' are not the same thing — the steering rules run on top of Rule 10.

Rule 11: Rules 11 to 18 apply to vessels in sight of one another only.Trap · if you have her on radar in fog but cannot see her, Rules 11–18 do NOT apply — you are in Rule 19, with no give-way/stand-on vessel.

Rule 12: (a)(i) when each has the wind on a different side, the vessel with the wind on the port side keeps out of the way; (a)(ii) when both have the wind on the same side, the vessel to windward keeps out of the way of the one to leeward; (a)(iii) if a port-tack vessel sees a vessel to windward and cannot tell whether that vessel is on port or starboard, she keeps out of the way. Windward side is the side opposite that on which the mainsail is carried (12(b)).Lead · port gives way to starboard; if same tack, windward gives way to leeward.

Rule 13 — overtaking overrides everything in Rules 4–18, including Rule 12. The overtaking sailing vessel keeps clear until finally past and clear, whatever the tacks or the wind side.Trap · don't reach for the port-tack/windward answer when it's actually an overtaking.

Rule 13(b): overtaking is coming up on another vessel from more than 22.5° abaft her beam — i.e. at night you would see only her sternlight and neither sidelight. (a) Rule 13 overrides anything in Section II. (d) Any subsequent alteration of bearing shall not make the overtaking vessel a crossing vessel or relieve her of the duty to keep clear until finally past and clear.Trap · once overtaking, always overtaking — you keep out of the way until well past.

Rule 13(c): when in doubt whether she is overtaking, a vessel shall assume that she is and act accordingly — i.e. keep out of the way.Lead · doubt resolves in favour of being the overtaking (give-way) vessel.

Yes — Rule 13(d): once overtaking, a later change of bearing does not make you a crossing vessel or relieve you of the duty to keep clear until finally past and clear. Seeing a sidelight appear as she manoeuvres does not restart the situation as a crossing.Lead · the status is fixed at the moment of overtaking and only ends when you are well past.

By the lights you can see. Overtaking (Rule 13(b)) is coming up from more than 22.5° abaft her beam — the position from which, at night, you would see her sternlight but neither sidelight. See a sidelight and you are forward of that line — a crossing (or head-on) case.Tip · sternlight only = overtaking; a sidelight in view = not overtaking.

Rule 14: when two power-driven vessels meet on reciprocal or nearly reciprocal courses so as to involve risk of collision, each shall alter course to starboard so that each passes on the port side of the other (pass port-to-port). It exists when, by night, you see the other's two masthead lights in a line (or nearly) and/or both sidelights, or by day the corresponding aspect. Rule 14(c): if in doubt whether a head-on situation exists, assume it does and act accordingly.Lead · both alter to starboard, pass port-to-port; doubt = treat as head-on.

Rule 14 bites only when there is risk of collision. If you are certainly passing clear (green-to-green) with no risk, no action is required. But Rule 14(c): if in any doubt whether a head-on situation exists, assume it does and alter to starboard.Trap · a marginal starboard-to-starboard pass in doubt should be resolved by a positive starboard alteration to a clean port-to-port, not by hoping.

Rule 15: the vessel which has the other on her own starboard side shall keep out of the way and shall, if the circumstances admit, avoid crossing ahead of the other vessel.Lead · 'if to starboard, keep out of her way' — and pass under her stern, don't cut across her bow.

Rule 15 says avoid crossing ahead 'if the circumstances of the case admit' — it is a strong preference, not absolute. The seamanlike action is usually a bold starboard alteration to pass under her stern; if passing astern is genuinely impossible, a substantial starboard alteration to open the situation is still preferred to a port turn across her bow.Watch · a port alteration that takes you across her head is the classic wrong answer.

Rule 16: the give-way vessel shall, so far as possible, take early and substantial action to keep well clear.Lead · early and substantial — not a token last-minute nudge.

Rule 17: (a)(i) the stand-on vessel shall keep her course and speed. (a)(ii) She may take action to avoid collision as soon as it becomes apparent the give-way vessel is not taking appropriate action. (b) When collision cannot be avoided by the give-way vessel's action alone, she shall take such action as will best avoid collision. (c) A power-driven vessel taking action in a crossing situation should, if the circumstances admit, not alter course to port for a vessel on her own port side.Trap · don't turn to port for the crossing vessel on your port bow — you'd turn into her.

'May' (17(a)(ii)): as soon as it is apparent the give-way vessel is not taking appropriate action. 'Must' (17(b)): when collision cannot be avoided by the give-way vessel's action alone — you are then *obliged* to take the best avoiding action.Lead · an early permissive stage, then a mandatory stage when only your action can prevent collision.

No — Rule 17(c): a power-driven vessel taking action in a crossing situation shall, if the circumstances admit, not alter course to port for a vessel on her own port side. Turning to port would swing you across her intended track.Tip · stand-on early action is normally a bold starboard alteration or a marked reduction of speed.

No — Rule 17(d): the taking of action by the stand-on vessel does not relieve the give-way vessel of her obligation to keep out of the way. Both are now acting; the give-way vessel is still bound.Lead · your last-ditch action never transfers the blame to you.

Rule 18 — 'pecking order' (each keeps out of the way of those above): a power-driven vessel keeps clear of NUC, RAM, fishing, and sailing; a sailing vessel keeps clear of NUC, RAM, and fishing; a fishing vessel keeps clear of NUC and RAM. A vessel constrained by her draught (Rule 18(d)) — every vessel other than NUC/RAM should, if circumstances admit, avoid impeding her safe passage. A seaplane/WIG keeps well clear of all and avoids impeding. Memory aid: 'New Reels Feel So Practical' — NUC, RAM, Fishing, Sailing, Power.Trap · the order does NOT override Rule 13 overtaking or Rules 9/10 in a channel/TSS.

Not in the pecking order sense. A CBD is a power-driven vessel; Rule 18(d) only asks other vessels to avoid impeding her safe passage 'if the circumstances of the case admit' — it does not lift her above fishing/sailing/RAM/NUC.Trap · CBD is a request not to impede, not a promotion above the RAM/fishing tiers.

The sailing vessel keeps clear. Rule 13 (overtaking) overrides Rule 18. The 'power keeps clear of sail' order applies only when they meet or cross, not when the sailing vessel is the one coming up from astern.Trap · this is a favourite — candidates reflexively make the power vessel give way.

No — she shows her RAM lights (red-white-red) plus the two all-round red / two all-round green obstruction lights of Rule 27(d), not the ordinary anchor lights of Rule 30. The obstruction lights tell you which side is foul and which side to pass.Watch · RAM signals replace the anchor signals for a vessel restricted in her ability to manoeuvre while working.

Rule 19 (vessels not in sight of one another in or near an area of RV): there is NO stand-on vessel — every vessel navigates with caution at safe speed, engines ready. A vessel which detects by radar alone another vessel shall determine if a close-quarters situation is developing and/or risk of collision exists; if so, take avoiding action in ample time. That action, so far as possible, shall avoid (i) an alteration of course to PORT for a vessel forward of the beam (other than one being overtaken), and (ii) an alteration of course TOWARDS a vessel abeam or abaft the beam.Lead · no give-way/stand-on in fog — but don't turn to port for something ahead, and don't turn towards something abeam/astern.

Rule 19(e): except where it has been determined that a risk of collision does not exist, every vessel which hears apparently forward of her beam the fog signal of another vessel, or which cannot avoid a close-quarters situation with a vessel forward of the beam, shall reduce her speed to the minimum at which she can be kept on course — and if necessary take all her way off — and in any event navigate with extreme caution until danger of collision is over.Lead · slow to steerage way (or stop) and proceed with extreme caution.

Yes — Rule 19(d)(i) expressly excepts 'a vessel being overtaken': the bar on altering to port for a vessel forward of the beam does not apply to overtaking. So in fog you may alter to port to overtake if that is the better side.Tip · the port-alteration restriction protects head-on/crossing geometry, not an overtaking you are deliberately carrying out.

Yes — the instant you are 'in sight of one another' (Rule 3(k)), Section II (Rules 11–18) takes over and there is now a give-way and a stand-on vessel. Re-appraise immediately: a situation you were handling as 'both give way' under Rule 19 becomes a defined crossing/head-on/overtaking case.Watch · the changeover is abrupt and is a common point of confusion.

Rule 20: lights shall be exhibited from sunset to sunrise, and in restricted visibility (and may be shown in all other circumstances when considered necessary). Shapes are exhibited by day. The Rules on lights must be complied with in all weathers.Lead · lights sunset–sunrise and in RV; shapes by day.

Rule 21: masthead light — white, over an arc of 225°, from right ahead to 22.5° abaft the beam each side. Sidelights — green (stbd)/red (port), each 112.5°, from ahead to 22.5° abaft the beam. Sternlight — white, 135°, 67.5° from right aft on each side. All-round light — 360°. Towing light — yellow, same characteristics as the sternlight (135°).Lead · 225 + 112.5 each side matches; stern 135 fills the rest to 360.

Rule 22 — range depends on the vessel's length. Vessels ≥50 m: masthead 6 miles, sidelights 3, stern/towing/all-round 3. Vessels 12–50 m: masthead 5 (3 if <20 m), sidelights 2, others 2. Vessels <12 m: masthead 2, sidelights 1, others 2.Lead · bigger ship, brighter lights — 6/3/3 for the big ones.

Rule 23(a): a power-driven vessel under way shows a masthead light forward; a second masthead light abaft of and higher than the forward one (vessels <50 m need not, but may); sidelights; and a sternlight. A vessel <12 m may instead show one all-round white light and sidelights (23(d)). An air-cushion vessel in non-displacement mode also shows an all-round flashing yellow light; a WIG on take-off/landing/near the surface shows a high-intensity all-round flashing red light.Trap · the second masthead light is compulsory only at 50 m and over.

A power-driven vessel ≥50 m, seen from astern (or fine on the quarter) — you see both masthead lights and the sternlight but the sidelights are screened from view abaft the beam. No yellow towing light means she is not towing.Lead · two masthead + sternlight, no sidelights = a big power-driven vessel end-on going away from you.

Rule 24(a): a power-driven vessel towing shows two masthead lights in a vertical line (three if the length of the tow, measured from the stern of the towing vessel to the after end of the tow, exceeds 200 m), sidelights, a sternlight, a towing (yellow) light above the sternlight, and — if the tow exceeds 200 m — a diamond shape where best seen. The vessel being towed shows sidelights and a sternlight (and a diamond if the tow exceeds 200 m).Lead · normal tow = 2 masthead + yellow towing light; tow over 200 m = 3 masthead + diamond both ends.

Rule 25(e): a vessel proceeding under sail when also being propelled by machinery shall exhibit forward, where it can best be seen, a conical shape, apex downwards. It matters because she is then a power-driven vessel for the Rules (Rule 3) and loses her sailing-vessel status in the Rule 18 order.Trap · engine on = power-driven, even with sails set — hence the cone.

Rule 26: a vessel trawling (dragging a dredge/apparatus through the water) shows an all-round GREEN over all-round WHITE in a vertical line, plus (when making way) sidelights and a sternlight; ≥50 m also a masthead light abaft and higher than the green. A vessel engaged in fishing other than trawling shows all-round RED over WHITE, and if her gear extends more than 150 m horizontally, an all-round white light or a cone apex-up in the direction of the gear. Day shapes: two cones apices together.Lead · 'green over white, trawling in sight; red over white, fishing at night.'

White over red = pilot vessel (Rule 29). Red over white = a vessel fishing, other than trawling (Rule 26). Green over white = trawling. The order of the colours is the whole answer.Tip · mnemonics — 'white over red, pilot ahead'; 'red over white, fishing tonight'; 'green over white, trawling in sight'.

Rule 27: NUC — two all-round RED in a vertical line, plus sidelights/sternlight when making way; day shape two balls. RAM — red-white-red all-round in a vertical line, plus masthead/side/stern lights as appropriate; day shape ball-diamond-ball. RAM engaged in dredging/underwater ops additionally shows two all-round red (or two balls) on the obstructed side and two all-round green (or two diamonds) on the side a vessel may pass. A vessel engaged in diving operations, unable to show the full RAM lights, shows the ball-diamond-ball plus a rigid replica of the International Code flag 'A'.Lead · two reds = NUC; red-white-red = RAM; add reds/greens to show which side to pass.

Two all-round reds = Not Under Command (Rule 27(a)). Three all-round reds = Constrained By her Draught (Rule 28). Count carefully — the difference of one light changes both the meaning and your obligation.Trap · NUC you must keep clear of as a power-driven vessel; CBD you should merely avoid impeding 'if circumstances admit'.

Restricted in her Ability to Manoeuvre (Rule 27(b)). No — she cannot keep out of your way; that is the whole point of the signal, so YOU keep clear (Rule 18). If she also shows two reds / two greens (Rule 27(d)) she is dredging or on underwater work — pass on the two-green side.Lead · red-white-red 'restricted in the middle' — give her a wide berth.

Rule 28: a vessel constrained by her draught may, in addition to the lights for a power-driven vessel under way, exhibit three all-round RED lights in a vertical line, or a cylinder (day shape).Trap · it is permissive ('may') and additional to her normal steaming lights — and CBD status only applies where depth and width available make it so; she is not RAM or NUC.

Rule 29: a vessel engaged on pilotage duty shows, at or near the masthead, an all-round WHITE over an all-round RED in a vertical line; when under way, sidelights and a sternlight in addition; at anchor, the anchor light(s) in addition to the white-over-red.Lead · 'white over red, pilot ahead.'

Rule 30: a vessel at anchor shows, where best seen, a forward all-round white light and another lower at/near the stern (or, if <50 m, one all-round white light where best seen). ≥100 m shall, and others may, use available working lights to illuminate the decks. Day shape: one black ball forward. A vessel <7 m at anchor not in or near a narrow channel, fairway, anchorage or where other vessels normally navigate need not show anchor lights/shape. A vessel aground shows the anchor lights plus two all-round red in a vertical line, and by day three balls.Lead · ball forward / all-round white(s); aground = two reds and three balls.

Aground — Rule 30(d): a vessel aground shows, by day, three balls in a vertical line (by night, the anchor light(s) plus two all-round red lights).Trap · one ball = at anchor; three balls = aground; don't confuse the count.

No — Rule 30(e): a vessel under 7 m at anchor, not in or near a narrow channel, fairway or anchorage or where other vessels normally navigate, need not show the anchor light or shape.Watch · the exemption evaporates the moment she is in or near a channel/anchorage/traffic.

Rule 31: where it is impracticable for a seaplane or a WIG craft to exhibit lights and shapes of the characteristics or in the positions prescribed, it shall exhibit lights and shapes as closely similar in characteristics and position as is possible.Lead · as near to the Rules as practicable.

Rule 32: a short blast is about one second's duration; a prolonged blast is from four to six seconds' duration. 'Whistle' means any sound-signalling appliance capable of the prescribed blasts and complying with Annex III.Lead · short ≈ 1 s, prolonged = 4–6 s.

Rule 33: a vessel ≥12 m shall be provided with a whistle; ≥20 m a bell in addition; ≥100 m a gong in addition, the tone/sound of which cannot be confused with the bell. A vessel <12 m need not carry these but if not, shall have some other means of making an efficient sound signal.Lead · whistle at 12 m, bell at 20 m, gong at 100 m.

Rule 34 (power-driven, in sight, manoeuvring as authorised/required): one short — 'I am altering to starboard'; two short — 'altering to port'; three short — 'operating astern propulsion'. Overtaking in a narrow channel (34(c)): two prolonged + one short — 'intend to overtake on your starboard'; two prolonged + two short — 'on your port'; vessel to be overtaken agrees with prolonged–short–prolonged–short (Morse 'C'). Doubt (34(d)): at least five short and rapid blasts — may be supplemented by five short flashes. Bend (34(e)): one prolonged on approaching a blind bend, answered by one prolonged.Lead · 1/2/3 short for helm; five short for doubt; one prolonged at a blind bend.

Rule 34(d): the 'doubt' or 'wake-up' signal — at least five short and rapid blasts, used when either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken to avoid collision. It may be supplemented by at least five short and rapid flashes of light.Lead · 'I don't understand what you're doing / I doubt you're doing enough.'

No — Rule 34 manoeuvring signals apply only to vessels IN SIGHT of one another. In restricted visibility you are under Rule 35 (fog signals), not Rule 34. Sounding 'one short' for a contact you cannot see would be meaningless and wrong.Trap · manoeuvring signals need visual contact; fog signals do not.

Rule 34(d): at least five short and rapid blasts — the doubt signal — used whenever you doubt the other's intentions or that she is taking sufficient action. Taking your own avoiding action does not replace it; if in doubt, sound it (and you may add five short flashes).Lead · when in doubt, five short — say so, don't just manoeuvre silently.

Rule 35: power-driven making way — one prolonged every ≤2 min; power-driven under way but stopped, not making way — two prolonged (≈2 s apart) every ≤2 min. NUC/RAM/CBD/sailing/fishing/towing vessel — one prolonged followed by two short, every ≤2 min. Vessel being towed (if manned) — one prolonged + three short, immediately after the towing vessel, when practicable. At anchor — rapid ringing of the bell ~5 s every ≤1 min (≥100 m: bell forward then gong aft); may also sound one short–one prolonged–one short to warn. Aground — three separate bell strokes, then the anchor bell signal, then three strokes.Lead · one prolonged = making way; two prolonged = stopped; 'prolonged + two short' covers the whole restricted/constrained family.

It could be any of: a vessel NUC, RAM, constrained by draught, sailing, fishing, or towing/pushing (Rule 35(c)). You cannot tell which from the sound alone. So treat her as a vessel you must keep clear of, navigate at safe speed with extreme caution, and be ready to reduce to bare steerage (Rule 19(e)).Trap · don't try to name a single type — the signal is deliberately shared by the whole 'can't easily get out of your way' family.

Rule 35(b): two prolonged blasts (about two seconds apart), every not more than two minutes — a power-driven vessel under way but STOPPED and making no way through the water. One prolonged (35(a)) would mean she is making way.Tip · count the prolonged blasts — one = making way, two = stopped.

Rule 35(g): a vessel at anchor rings the bell rapidly for about 5 seconds every minute; if 100 m or more in length she sounds the bell forward AND the gong aft. The gong therefore tells you she is a large vessel (≥100 m) at anchor.Lead · bell + gong = a big ship at anchor; bell alone = a smaller one.

Rule 36: any vessel may make light or sound signals to attract attention, provided they cannot be mistaken for any signal authorised elsewhere in the Rules, or direct a searchlight in such a way as to embarrass another vessel. High-intensity intermittent or revolving lights (e.g. strobes) are to be avoided.Lead · attract attention — but never in a way that mimics a Rules signal or dazzles the other vessel.

Rule 37: when a vessel is in distress and requires assistance she shall use or exhibit the signals described in Annex IV.Lead · distress = the Annex IV signals (e.g. SOS, Mayday, red parachute flare, NC flags, continuous fog-signal sounding, etc.).

No — an inverted ensign is NOT one of the Annex IV distress signals, though it is sometimes used informally. Rule 37 recognises only the signals listed in Annex IV (Mayday, SOS, NC flags, red parachute/hand flare, continuous fog-signal sounding, EPIRB/SART, DSC alert, etc.).Trap · the inverted-ensign answer is a classic examiner bait — don't take it.

Rule 38 grandfathers vessels (or vessels under construction) built before the entry into force of the 1972 Regulations, giving them time-limited exemptions from certain requirements — e.g. repositioning of lights, changed sound-signal appliance specifications — provided they comply with the earlier 1960 Regulations.Lead · transitional relief for older ships from specific fittings, on stated timescales.

Rule 39 (added later) is the Definitions rule for Part F (Verification of compliance): it defines 'audit', 'Audit Scheme', 'Code' and related terms for the IMO Member State Audit Scheme.Lead · it's the audit-scheme definitions, not a steering or lights rule.

Rule 40 (Part F): Contracting Parties shall use the provisions of the Code for Implementation in the performance of audits under the IMO Member State Audit Scheme.Lead · it makes the III Code / audit obligations binding on the flag State.

Rule 41: each Contracting Party is subject to periodic audits by IMO to verify compliance with, and implementation of, this Convention.Lead · the flag-State audit provision closing Part F.

Annex I gives the technical detail for positioning and technical particulars of lights and shapes — vertical/horizontal spacing, screening, shape dimensions, colour specification, intensity and arcs. 'Height above the hull' is measured from the position of least freeboard vertically below the light.Lead · Annex I is the 'how high, how far apart, how bright' rulebook behind Rules 20–31.

Annex I §2: on a power-driven vessel ≥20 m the forward masthead light is at least 6 m above the hull (and if breadth exceeds 6 m, at least that breadth, but need not exceed 12 m). The after masthead light is at least 4.5 m vertically higher than the forward one, and horizontally separated by at least half the vessel's length (need not exceed 100 m), the forward one not more than a quarter of the length from the stem.Lead · forward masthead ≥6 m up; the after one ≥4.5 m higher and well aft.

Annex I §3: sidelights on a power-driven vessel ≥20 m shall be placed at a height above the hull not greater than three-quarters of that of the forward masthead light, and not so low as to be interfered with by deck lights. They are placed on the fore-and-aft centreline or, if combined (in vessels <20 m), at or near the centreline.Lead · sidelights below the masthead light, clear of deck-light interference.

Annex I §4/§6: where two or three all-round lights are shown in a vertical line, they are spaced not less than 2 m apart (the lowest, except for towing, not less than 4 m above the hull on a vessel ≥20 m). Shapes shall be black — a ball ≥0.6 m in diameter, a cone base ≥0.6 m; vertical spacing of shapes at least 1.5 m.Lead · all-round lights ≥2 m apart; shapes are black, ≥0.6 m, spaced ≥1.5 m.

Annex I §8 sets the luminous intensity of lights by a formula relating intensity to the required range of visibility (Rule 22), using an atmospheric transmissivity figure — so a 6-mile light must produce a defined minimum candela.Lead · ranges in Rule 22 come from the intensity formula in Annex I §8.

Annex I §9: sidelights must show the minimum required intensity from right ahead to 1–3° outside the prescribed sector, and cut off practically at the 22.5° abaft-beam limit. Vertically (§10), the lights must show the required minimum intensity through ±5° (unlit vessels ±7.5° reduced) of the horizontal.Lead · tight cut-off outboard, a few degrees of vertical spread for the ship's roll.

Annex I §7: the colour of all navigation lights shall conform to the chromaticity standards defined by boundary coordinates (CIE) for white, green, red and yellow.Lead · the colours are fixed by CIE chromaticity limits, not judged by eye.

Annex I §5: sidelights shall be fitted with inboard screens painted matt black to prevent the green being seen on the port side or the red on the starboard side. Combined lanterns (vessels <20 m) need a division/screen.Lead · matt-black inboard screens so a sidelight is never seen across the bow to the wrong side.

Annex I §12: the all-round white manoeuvring light, if fitted, is placed in the same fore-and-aft vertical plane as the masthead light(s), where practicable at least 2 m vertically above the forward masthead light — and not less than 2 m above/below the after masthead light — provided it is not less than 2 m above/below the forward masthead light.Lead · the manoeuvring light sits in line with, and clear of, the masthead lights.

Annex I §2(a)(iii)/§13: on high-speed craft the masthead-light height may be reduced in relation to the breadth as permitted, to keep windage and structure practical, so long as the arcs and separations are met.Lead · HSC get a relaxation on masthead height tied to breadth.

Annex I §14: the construction of lights and shapes and the installation of lights on board the vessel shall be to the satisfaction of the appropriate authority of the flag State.Lead · lights and their fitting must be type-approved by the flag Administration.

Annex I §2(g)/§3(b): on vessels <20 m the lights may be placed at reduced heights, but sidelights combined in one lantern shall be at least 1 m below the masthead light, and lights carried on a mast shall be positioned so as not to be obscured.Lead · small craft get lower minimum heights, keeping the sidelights below the masthead light.

Annex I (with Rule 23(c)): a WIG craft, only when taking off, landing and in flight near the surface, exhibits a high-intensity all-round flashing RED light, in addition to the power-driven vessel lights.Lead · WIG in ground-effect flight = high-intensity flashing red.

That the candidate knows the arcs, minimum ranges (Rule 22) and the vertical/horizontal geometry that make lights unambiguous — so an observer can read a vessel's aspect, type and size correctly at night.Lead · Annex I exists so a light picture is never ambiguous about aspect or vessel type.

Annex II: Additional signals for fishing vessels fishing in close proximity — extra all-round lights so trawlers/purse-seiners working together don't misread each other's gear. They apply only to fishing vessels engaged in fishing in close proximity to others; they are additional to Rule 26.Lead · Annex II is the 'fishing fleet working together' extra lights, over and above Rule 26.

Annex II §2: vessels trawling may show two all-round WHITE in a vertical line when shooting their nets; white over red when hauling; two red in a vertical line when the net has come fast upon an obstruction. Pair trawlers may show a searchlight forward and in the direction of the other of the pair.Lead · white-white shooting, white-red hauling, red-red fast on an obstruction.

Annex II §3: vessels engaged in fishing with purse-seine gear may exhibit two all-round YELLOW lights in a vertical line, flashing alternately every second with equal light and occultation periods — shown only when hampered by their gear.Lead · two alternately flashing yellow lights = purse seiner hampered by her gear.

Annex III: Technical details of sound signal appliances — the fundamental frequency, sound pressure level/range, and directional properties of whistles, and the construction of bells and gongs.Lead · Annex III is the engineering spec behind Rules 32–33 (how loud, what pitch, how far a whistle must be heard).

Annex III §1: fundamental frequency 70–700 Hz; the audible range is set so a whistle on a vessel ≥200 m has a fundamental in the 70–200 Hz band audible ~2 miles, 75–200 m in the 130–350 Hz band, and <75 m in the 250–700 Hz band audible ~0.5 mile. Larger vessels have lower-pitched, longer-range whistles.Lead · the bigger the ship, the deeper and further-carrying the whistle.

Annex III §2: the bell or gong (or other appliance with similar sound characteristics) — the sound pressure level not less than 110 dB at 1 m; the bell/gong of corrosion-resistant material designed to give a clear tone; for a vessel ≥20 m the bell shall be not less than 300 mm in diameter.Lead · bell ≥300 mm mouth on vessels ≥20 m, ≥110 dB at 1 metre.

Annex IV signals, used or exhibited together or separately, indicate distress and need of assistance: a gun/explosive signal fired at ~1-minute intervals; continuous sounding of any fog-signal apparatus; rockets/shells throwing red stars one at a time; SOS by any signalling method; 'MAYDAY' by radiotelephony; the flag signal NC; a square flag with a ball above or below; flames on the vessel (burning tar/oil barrel); a red parachute or hand flare; orange smoke; slowly raising and lowering outstretched arms; DSC distress alert; EPIRB/SART; and approved signals via GMDSS.Trap · an inverted national ensign is a common exam wrong-answer — it is NOT an Annex IV distress signal.