ONDECK
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OOW Oral Prep
Module 03 — OOW 3000 GT Oral Preparation
COLREGS
International Regulations for Preventing Collisions at Sea — the rules, lights, shapes and sound signals, plus the interpretation, precedence and nuances the examiner actually probes
COLREGS apply to all vessels on the high seas and all waters connected to the high seas. A thorough knowledge is mandatory for the OOW — not optional background reading. In the oral, COLREGS is a trip-wire subject: there is no leeway. One unsafe answer fails the exam regardless of how the rest went.
Structure of the COLREGS
| Part | Covers | Key Rules |
|---|---|---|
| Part A | General | Rules 1–3 — Application, responsibility, definitions |
| Part B | Steering and Sailing Rules | Rules 4–19 — Conduct in all conditions and restricted visibility |
| Part C | Lights and Shapes | Rules 20–31 — What to show and when |
| Part D | Sound and Light Signals | Rules 32–37 — Signals for manoeuvring, distress, restricted visibility |
| Annexes I–IV | Technical specifications | Positioning and visibility of lights, sound signal specs, distress signals |
How to Read the Rules — Start With Visibility
Part B is not a flat list of nineteen rules. It is three sections, and which section you are in changes everything. This is the single most important structural fact in the COLREGS — and the one candidates miss.
SECTION I — Rules 4–10: apply in ANY condition of visibility · SECTION II — Rules 11–18: apply ONLY to vessels in sight of one another · SECTION III — Rule 19: applies ONLY in or near restricted visibility, to vessels NOT in sight
Master's Note — The First Question Is Always Visibility
Before you name a rule, decide which section you are in. "In sight of one another" means observed visually — Rule 3(k). A radar contact in fog is not in sight. Stand-on, give-way and the Rule 18 hierarchy exist only inside Section II — between vessels that can actually see each other. Get the section wrong and every answer that follows is wrong.
Master's Note — Section I Never Switches Off
Rules 4–10 — lookout, safe speed, risk of collision, action to avoid, narrow channels, TSS — apply in every condition of visibility, alongside whichever of Section II or III applies. Fog does not suspend Rule 5. It sharpens it.
Master's Note — There Is No Stand-On Vessel in Fog
In restricted visibility there is no stand-on vessel, no give-way vessel, and no hierarchy. Every vessel is obliged to take avoiding action under Rule 19. Answering a fog scenario with "I am the stand-on vessel" is an instant-fail answer in the oral — and the same mental error sinks ships at sea. If you are in doubt whether the other vessel can see you, act under Rule 19.
The Order of Authority — What Overrides What
- Rule 2 sits over everything. 2(a): nothing exonerates you from the consequences of neglecting any precaution required by the ordinary practice of seamen or the special circumstances of the case. 2(b): you may depart from the rules — but only when necessary to avoid immediate danger. Rule 2 is not a get-out clause. Courts read it against the vessel that quotes it.
- Special local rules can modify the COLREGS. Rule 1(b) — harbour authorities, rivers and inland waterways may have their own rules. Check the pilot book before you arrive, not after the five short blasts.
- Rule 18 opens with its own exception: "Except where Rules 9, 10 and 13 otherwise require." Overtaking, narrow channels and traffic separation schemes all sit above the vessel hierarchy.
- Rule 13 beats everything in Section II. An overtaking vessel keeps clear of the vessel being overtaken regardless of type — a sailing vessel overtaking a power-driven vessel is the give-way vessel.
- Once overtaking, always overtaking. Rule 13(d): no subsequent change of bearing turns you into a crossing vessel or relieves you of keeping clear — until you are finally past and clear.
Master's Note — "Not to Impede" Is Not "Give Way"
Rule 8(f) is its own regime and the exam loves it. A vessel required not to impede (Rules 9, 10, 18(d)) must take early action to allow sufficient sea-room — before risk of collision even exists. If risk of collision develops anyway, she is not relieved of that obligation — 8(f)(ii) — and the vessel whose passage is not to be impeded remains fully bound by the steering rules — 8(f)(iii). A ship in a TSS lane holds no priority pass over a vessel crossing from her starboard side, and Rule 10 says so itself: it does not relieve any vessel of her obligations under any other rule.
Master's Note — Crossing vs Narrow Channel: The Ever Smart Case
Ever Smart / Alexandra 1 (UK Supreme Court, 2021) — the first collision case to reach the UK's highest court in around fifty years. Two holdings worth carrying into the exam room: the crossing rules are to be applied strictly and are only displaced where there is compelling necessity; and the crossing rule engages even if the give-way vessel is not on a steady course — what matters is a steady bearing. A vessel waiting off a channel entrance and a vessel approaching it are in a crossing situation unless the approaching vessel is on her final approach, shaping her course to enter the channel.
The Doubt Clauses — The Rules Decide For You
The rule-makers built the answer to ambiguity into the rules themselves. Every doubt clause resolves the same way — towards the more cautious obligation.
| Doubt | The rule's answer | Rule |
|---|---|---|
| Is there risk of collision? | If there is any doubt — such risk shall be deemed to exist | 7(a) |
| Am I overtaking or crossing? | Assume you are overtaking and keep clear | 13(c) |
| Is this head-on or crossing? | Assume it is head-on and act accordingly — alter to starboard | 14(c) |
| What is the other vessel doing? | Sound at least five short and rapid blasts | 34(d) |
| Can the other vessel see me? | If not certain you are in sight of one another — act under Rule 19 | 19(a) |
"If in doubt, there is no doubt — act." That seaman's aphorism is a direct restatement of Rules 7(a), 13(c) and 14(c). Answer the examiner the same way the rules answer you: take the cautious obligation, early.
Part B — Steering and Sailing Rules: The Critical Rules
| Rule | Subject | Key content |
|---|---|---|
| Rule 5 | Lookout | Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision |
| Rule 6 | Safe Speed | Every vessel shall at all times proceed at a safe speed — visibility, traffic density, manoeuvrability, background lights, wind/sea/current, draught vs depth all considered; radar-fitted vessels add radar limitations, range scale, clutter, number and movement of targets. No fixed speed — it is situational |
| Rule 7 | Risk of Collision | Use all available means — radar plotting, systematic compass bearings. A steady compass bearing with decreasing range = risk of collision. Scanty information = assume risk exists |
| Rule 8 | Action to Avoid Collision | Action shall be taken in accordance with the rules of this Part (8(a), added 2007 — Rule 8 is not a licence to act contrary to the steering rules), positive, made in ample time, large enough to be readily apparent to the other vessel visually or by radar. Avoid a succession of small alterations. Course alteration alone must not create another close-quarters situation — 8(c). Slackening speed, stopping or reversing is action too — 8(e). Check action is effective until past and clear |
| Rule 9 | Narrow Channels | Keep to the starboard side. Vessels under 20m and sailing vessels shall not impede vessels that can only navigate safely within the channel. Do not cross if crossing impedes a vessel that can only navigate inside the channel — 9(d) |
| Rule 10 | Traffic Separation Schemes | Use the appropriate lane. Enter/leave at the ends if possible. Cross on a heading as nearly as practicable at right angles to the traffic flow. Vessels under 20m and sailing vessels shall not impede power-driven vessels in the lane. Rule 10 does not relieve any vessel of any other rule |
| Rule 13 | Overtaking | Any vessel overtaking — coming up from more than 22.5° abaft the other's beam — shall keep out of the way until finally past and clear. Overtaking vessel is always give-way, regardless of vessel type |
| Rule 14 | Head-On | When two power-driven vessels meet on reciprocal or nearly reciprocal courses — both alter to starboard, pass port to port |
| Rule 15 | Crossing | When two power-driven vessels are crossing — the vessel that has the other on its starboard side shall give way, and shall avoid crossing ahead of the other vessel |
| Rule 16 | Give-Way Vessel | Shall take early and substantial action to keep well clear |
| Rule 17 | Stand-On Vessel | Shall keep course and speed. May take action when it becomes apparent the give-way vessel is not acting — 17(a)(ii). Shall take action when collision cannot be avoided by the give-way vessel alone — 17(b). See the three stages below |
| Rule 18 | Vessel Hierarchy | "Except where Rules 9, 10 and 13 otherwise require" — see table below for who gives way to whom |
| Rule 19 | Restricted Visibility | Safe speed adapted to the conditions. Engines ready for immediate manoeuvre. If close-quarters developing from a radar-detected vessel — take avoiding action in ample time, avoiding: alteration to port for a vessel forward of the beam; alteration towards a vessel abeam or abaft the beam |
Rule 17 — The Three Stages of Stand-On
There is no "right of way" anywhere in the COLREGS. Standing on is an obligation, not a right — and it comes in stages. Know them in order; the examiner will walk you through a crossing that deteriorates, and they want to hear the stages change.
| Stage | Obligation | Rule |
|---|---|---|
| 1 — Stand on | Shall keep her course and speed | 17(a)(i) |
| 2 — May act | May take action by her manoeuvre alone, as soon as it becomes apparent the give-way vessel is not taking appropriate action. Sound at least five short blasts first — Rule 34(d) | 17(a)(ii) |
| 3 — Shall act | When so close that collision cannot be avoided by the give-way vessel alone — shall take whatever action best aids avoiding collision | 17(b) |
Master's Note — Never Port for a Vessel on Your Port Side
When you act at stage 2 in a power-driven crossing, Rule 17(c): do not alter to port for a vessel on your own port side, if circumstances admit. The logic: the moment she finally honours Rule 15 and comes to starboard, you have turned into her and the CPA collapses. Court findings repeatedly hang the mariner who went to port. In open water, power on power, the working rule is simple: alterations are to starboard.
Rule 17(d): nothing in Rule 17 relieves the give-way vessel of her obligation to keep out of the way. The stand-on vessel acting does not swap the roles.
Rule 18 — Vessel Hierarchy (Give Way Order)
Not Under Command → Restricted in Ability to Manoeuvre → Constrained by Draught → Fishing → Sailing → Power-Driven
Each vessel gives way to all vessels above it in the list. Power-driven gives way to all others. Exceptions built into the rule itself: Rule 18 opens "Except where Rules 9, 10 and 13 otherwise require" — overtaking, narrow channels and TSS obligations sit above the hierarchy.
Master's Note — Where the Hierarchy Does Not Reach
The hierarchy applies only between vessels in sight of one another — it is dead in fog. It says nothing about anchored vessels. And constrained by draught is the soft rung: other vessels shall "avoid impeding the safe passage" of a CBD vessel if the circumstances of the case admit — 18(d) — which is weaker than a give-way obligation. CBD applies to power-driven vessels only — Rule 3(h). NUC means an exceptional circumstance — steering gear failure, engine breakdown — not "we are drifting for lunch." Showing NUC lights for convenience is misuse and examiners know the difference.
"Sail always has right of way over power" is wrong four ways: sail gives way to NUC, RAM and vessels engaged in fishing — 18(b); a sailing vessel overtaking anything keeps clear — Rule 13; sail must not impede vessels in narrow channels, TSS lanes or a CBD vessel — Rules 9, 10, 18(d); and a sailing vessel motor-sailing is a power-driven vessel — Rule 3(c) — showing a cone point down by day — 25(e).
Rule 19 — Restricted Visibility, Properly Understood
- 19(a): applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. "Near" matters — clear on your side, fog bank ahead: the rule already applies.
- 19(b): safe speed adapted to the circumstances; a power-driven vessel shall have her engines ready for immediate manoeuvre.
- 19(d): radar-detected vessel, close-quarters developing or risk of collision — take avoiding action in ample time, and so far as possible avoid: (i) an alteration to port for a vessel forward of the beam (other than a vessel being overtaken); (ii) an alteration towards a vessel abeam or abaft the beam.
- 19(e): fog signal heard apparently forward of the beam, or close-quarters with a vessel forward of the beam that cannot be avoided — reduce speed to the minimum at which she can be kept on her course; if necessary take all her way off; navigate with extreme caution until the danger of collision is over.
Master's Note — Why 19(d) Bans Those Two Alterations
The prohibitions encode one assumption: the other vessel is probably altering to starboard, because that is what the rules train everyone to do. If you go port for a vessel forward of the beam while she comes starboard, you meet in the middle. If you turn towards a vessel abeam or abaft the beam, you close the range on a contact you cannot see. So in fog the default action for a vessel ahead is a bold alteration to starboard — and remember speed is an action: slowing down is often the better manoeuvre, and 19(e) may make it mandatory.
Part C — Lights: What to Show and When
| Light | Arc | Colour | Carried by |
|---|---|---|---|
| Masthead (steaming) | 225° — dead ahead to 22.5° abaft the beam each side | White | Power-driven vessels underway |
| Sidelights | 112.5° each — green (starboard), red (port) | Green / Red | All vessels underway |
| Sternlight | 135° — showing aft | White | All vessels underway |
| All-round white | 360° | White | At anchor; towing; pilot vessel; NUC / RAM at anchor |
| All-round green over white | 360° each | Green / White | Fishing vessel trawling — "green over white, trawling tonight" |
| All-round red over white | 360° each | Red / White | Fishing vessel other than trawling (lines, nets) — "red over white, fishing tonight" |
| Two all-round red (vertical) | 360° each | Red / Red | Not Under Command |
| Red white red (vertical) | 360° each | R / W / R | Restricted in Ability to Manoeuvre |
| Yellow flashing | 360° | Yellow | Air cushion vessel in non-displacement mode |
Master's Note — The Arcs Are a System, Not a List
Masthead 225° + sternlight 135° = 360°. Sidelights 112.5° each = the 225° masthead arc split in two. And the sternlight arc is the overtaking sector: Rule 13(b) defines overtaking as coming up from more than 22.5° abaft the other vessel's beam — exactly where, at night, you can see only her sternlight. So the seaman's check: if you can see her sternlight and neither sidelight, you are overtaking — and you are the give-way vessel, whatever you are.
The lights answer formula: type → length band → motion → aspect → fog signal. "Power-driven vessel, under 50 metres, making way, crossing from starboard to port — her fog signal would be one prolonged blast every two minutes." Deliver it in that order, instantly. Hesitation on a lights card reads as unsafe.
At Anchor
- Under 50m: one all-round white light forward
- 50m and over: all-round white forward + all-round white aft
- May use working lights to illuminate decks
- Ball shape by day — forward
Aground
- Anchor lights PLUS
- Two all-round red lights (vertical) — forward
- Three balls (vertical) by day
Underway is not the same as making way. Underway — Rule 3(i) — means not at anchor, not made fast to the shore, not aground. A vessel drifting with engines stopped is underway but not making way — and her lights and fog signal change accordingly (two prolonged blasts, not one).
Part C — Day Shapes
| Shape | Meaning |
|---|---|
| One black ball | At anchor |
| Three black balls (vertical) | Aground |
| Two black balls (vertical) | Not Under Command |
| Ball, diamond, ball (vertical) | Restricted in Ability to Manoeuvre |
| Cone point down (forward) | Sailing vessel using engine — motorsailing |
| Diamond shape | Vessel or tow over 200m |
| Cylinder | Vessel constrained by draught |
Part D — Sound Signals
Manoeuvring Signals (in sight of each other)
- 1 short blast — altering course to starboard
- 2 short blasts — altering course to port
- 3 short blasts — operating astern propulsion
- 5 or more short blasts — doubt / danger signal
- 2 prolonged + 1 short — overtaking on starboard side
- 2 prolonged + 2 short — overtaking on port side
- 1 prolonged + 1 short + 1 prolonged + 1 short — agreement to be overtaken
Restricted Visibility Signals (Rule 35)
- 1 prolonged blast every 2 min — power-driven vessel making way
- 2 prolonged blasts every 2 min — power-driven vessel underway but stopped
- 1 prolonged + 2 short every 2 min — NUC, RAM, CBD, sailing, fishing, towing
- 1 prolonged + 3 short — last manned vessel of a tow
- Bell 5 sec every 1 min — vessel at anchor (100m+ also gong aft)
- Bell 5 sec + 3 bell strokes — vessel aground (before and after bell)
SHORT BLAST = about 1 second. PROLONGED BLAST = 4–6 seconds. Know this — the examiner will ask.
Master's Note — Manoeuvring Signals Are In-Sight Only
Rule 34 manoeuvring signals are exchanged between vessels in sight of one another. In fog you do not sound one short blast when altering for a radar contact — you sound your Rule 35 fog signal and nothing else. And Rule 34 signals are statements of action being taken — "I am altering to starboard" — not requests or proposals.
What Fails Candidates — The Examiner's Red Lines
Negotiating by VHF. MGN 324: using VHF to agree collision avoidance "is not always helpful and may even prove to be dangerous" — time lost making contact, misidentified vessels, and agreements that contravene the COLREGS. The MAIB has a name for the result: the VHF-assisted collision. The exam answer is always: comply with the rules, do not negotiate a passing arrangement.
Relying on AIS for collision avoidance. There is no provision for AIS anywhere in the COLREGS. Risk of collision is determined by systematic compass bearings and radar plotting — Rule 7(b). AIS also transmits course and speed over the ground, not through the water — set and drift make AIS aspect misleading. AIS aids identification; it does not replace a plot. A glance at a screen without a plot is "scanty information" — Rule 7(c) — and assumptions shall not be made on it.
Small alterations and silent intentions. Rule 8(b): action must be large enough to be readily apparent to the other vessel visually or by radar — a succession of small alterations shall be avoided. A 5° tweak looks decisive from your bridge and invisible on their radar trail. "Early and substantial" — Rule 16 — means the other vessel never has to wonder what you are doing.
Forgetting that speed is an action — and that the Master exists. Rule 8(e): slacken speed, stop, or reverse. Candidates over-favour the helm. In fog, 19(e) can make slowing mandatory. And calling the Master is an examined competence, not an admission of failure — "I am in doubt, I would call the Master" is a safe answer; bluffing is not.
Distress Signals Annex IV
Any one of the following indicates distress and need of assistance:
- Gun fired at intervals of about 1 minute
- Continuous sounding of fog signal apparatus
- Rockets or shells throwing red stars
- SOS by any means (Morse code)
- Mayday by radiotelephony
- International Code Signal NC
- Square flag above or below a ball
- Flames on the vessel (burning tar barrel)
- Orange smoke signal
- Slowly and repeatedly raising and lowering outstretched arms
- EPIRB alert
- Approved signals by radiocommunication systems (DSC / Inmarsat)
- Parachute flare — red
- Dye marker in the water
- High-intensity white light flashing (SOS)
Oral Exam Practice Questions
Question 1
Two power-driven vessels are crossing. Which gives way?
The vessel that has the other on its starboard side shall give way — Rule 15. It shall avoid crossing ahead of the stand-on vessel. The stand-on vessel shall maintain course and speed — Rule 17 — but may act as soon as it is apparent the give-way vessel is not acting — 17(a)(ii) — and must act when collision can no longer be avoided by the give-way vessel alone — 17(b). If acting, she should not alter to port for a vessel on her own port side — 17(c).
Question 2
What does Rule 19 require in restricted visibility?
Proceed at safe speed adapted to the circumstances with engines ready for immediate manoeuvre. There is no stand-on or give-way vessel — every vessel manoeuvres. If close-quarters is developing with a radar-detected vessel, take avoiding action in ample time, avoiding an alteration to port for a vessel forward of the beam (other than a vessel being overtaken) and an alteration towards a vessel abeam or abaft the beam — 19(d). On hearing a fog signal apparently forward of the beam, reduce to the minimum speed at which course can be kept, if necessary take all way off — 19(e).
Question 3
You see a vessel showing red over white all-round lights. What is it?
A vessel engaged in fishing other than trawling — Rule 26(c). "Red over white, fishing tonight; green over white, trawling tonight." If her outlying gear extends more than 150 metres, she shows an all-round white light in the direction of the gear. Full answer formula: type, making way or not from sidelights/sternlight, aspect — and her fog signal would be one prolonged plus two short blasts every two minutes.
Question 4
What sound signal do you make when you are at anchor in restricted visibility?
A rapid ringing of the bell for about 5 seconds at intervals of not more than one minute — Rule 35(g). Vessels 100m or more also sound a gong aft immediately after the bell. Vessels aground sound the bell signal preceded and followed by three separate and distinct strokes of the bell.
Question 5
A vessel overtakes your vessel on the starboard side in a narrow channel. What sound signal does it make?
Two prolonged blasts followed by one short blast — indicating intention to overtake on the starboard side (Rule 34(c)(i)). If you agree and it is safe to proceed, you respond with one prolonged, one short, one prolonged, one short blast. If you are in doubt, you sound five or more short blasts.
Question 6
You are in fog. Radar shows a vessel four miles off your starboard bow, steady bearing, decreasing range. Are you the give-way vessel?
Neither vessel is give-way or stand-on — we are not in sight of one another, so Section II does not apply. This is Rule 19. Close-quarters is developing, so I take avoiding action in ample time: a bold alteration to starboard — avoiding an alteration to port for a vessel forward of the beam, 19(d)(i) — and/or a reduction in speed. Engines ready for immediate manoeuvre, sounding my fog signal, plotting continuously until she is finally past and clear, and calling the Master if in any doubt.
Question 7
You are overtaking another vessel. As you draw up, the relative bearing changes until it looks like a crossing situation with you as stand-on. What are you?
Still the overtaking vessel. Rule 13(d): no subsequent alteration of the bearing between the two vessels shall make the overtaking vessel a crossing vessel, or relieve her of the duty of keeping clear of the overtaken vessel until she is finally past and clear. And by 13(c), if there had been any doubt whether I was overtaking, I assume I am and keep clear.
Question 8
You are a 30m yacht about to cross a narrow channel. A laden bulk carrier that can only navigate safely inside the channel is approaching. What are your obligations?
Rule 9(d) — I shall not cross if my crossing would impede her passage. The not-to-impede obligation means taking early action to allow sufficient sea-room — Rule 8(f)(i) — before any risk of collision develops. If risk of collision nevertheless arises, I am not relieved of my obligation — 8(f)(ii) — and both vessels remain bound by the steering and sailing rules — 8(f)(iii). She may sound at least five short and rapid blasts if she is in doubt of my intentions — Rule 34(d).