COLREGs & Watchkeeping

Before any give-way/stand-on mechanics, understand Rule 2, the rule of good seamanship. It states that nothing in the Rules exonerates a vessel, owner, master or crew from the consequences of neglecting any precaution required by the ordinary practice of seamen, or by the special circumstances of the case. In other words, compliance with every numbered rule does not by itself protect an officer who ignores the obvious. Examiners return to this rule constantly, because it is the safety net beneath the whole framework: no clever reading of Rule 17 rescues a watchkeeper who held course into an unmistakably dangerous situation.

The Rules are laid out in a deliberate order, and that order matters as much as the content. Rules 5 to 8 apply in any condition of visibility, to every vessel, before the steering-and-sailing mechanics of Rules 11 to 18 (which only bite when vessels are in sight of one another) and before Rule 19 (restricted visibility). A candidate who jumps straight to "who is give-way" has skipped the part of the syllabus examiners weight most heavily: lookout, safe speed, the test for risk of collision, and the character of the action to be taken.

Rule 5 requires a proper look-out by sight and hearing, and by all available means appropriate to the prevailing circumstances and conditions — radar, AIS, VHF, as well as eyes and ears — so that a full appraisal of the situation can be made. Rule 6 then asks for a safe speed, judged against a list of factors: visibility, traffic density, the vessel's stopping distance and turning characteristics, background lighting, sea state, and the set of any current. Neither rule gives a number. Both are judged after the fact against what a prudent officer would have done with the information available at the time, which is exactly why examiners probe them hard — there is no formula to hide behind.

Rule 7 gives the practical test for risk of collision: if the compass bearing of an approaching vessel does not appreciably change, risk exists. The same test applies to a radar plot, and the rule is explicit that assumptions must not be made on scanty information — especially scanty radar information. Where any doubt exists, risk of collision must be deemed to exist. Rule 8 then sets the character of the response: any action taken to avoid collision must be positive, made in ample time, and in accordance with good seamanship. A succession of small alterations is specifically to be avoided, and where there is room to manoeuvre, an alteration of course alone may be the most effective single action — because it is the one most readily seen by the other vessel, whether visually or on radar.

Once two power-driven vessels are in sight of one another, three situations are defined by the relative bearing at which each sees the other. Head-on (Rule 14) exists when vessels are meeting on reciprocal or nearly reciprocal courses so that each sees the other ahead or nearly ahead; both alter to starboard. Crossing (Rule 15) exists when the courses cross at an angle; the vessel that has the other on her own starboard side is give-way, and — so far as the circumstances of the case admit — must avoid crossing ahead of the other vessel. Overtaking (Rule 13) is defined not by bearing but by approach: a vessel coming up on another from more than 22.5° abaft that vessel's beam is overtaking, must keep clear until finally past and clear, and remains the give-way vessel throughout even if the geometry later starts to look like a crossing situation. Rule 13 is deliberately written to override Rules 14 and 15 whenever it applies.

Rule 16 obliges the give-way vessel to take early and substantial action to keep well clear. Rule 17 is the one most often misunderstood: the stand-on vessel's first duty is to keep her course and speed, but that duty is not unconditional. Once it becomes apparent that the give-way vessel is not taking appropriate action, the stand-on vessel may act; and once collision cannot be avoided by the give-way vessel's action alone, the stand-on vessel shall take whatever action best aids avoidance — action which should not, as a first choice, be an alteration to port for a vessel on her own port side. Rule 18 then ranks vessels by manoeuvrability rather than geometry, running from a vessel not under command, through one restricted in her ability to manoeuvre, one constrained by her draught, a vessel fishing, and a sailing vessel, down to a plain power-driven vessel — each giving way to every category above it on the list, subject always to Rules 9, 10 and 13.

Rule 19 does not modify the steering and sailing rules for fog — it replaces them. There is no give-way vessel and no stand-on vessel in restricted visibility, because the relative-bearing tests behind Rules 14 and 15 assume both vessels can see each other; by definition, in fog, they usually cannot. Every vessel must instead proceed at a safe speed adapted to the prevailing circumstances of restricted visibility, with engines ready for immediate manoeuvre, and must determine by radar, where fitted, whether a close-quarters situation or risk of collision is developing — a situation detected only by radar must still be acted on under Rules 7 and 8.

Two specific restrictions follow directly from the loss of the stand-on/give-way relationship. So far as possible, a vessel must avoid an alteration of course towards a vessel forward of the beam, other than for a vessel being overtaken, and must avoid an alteration of course towards a vessel abeam or abaft the beam. In practice this means: do not turn towards trouble you cannot see. If a close-quarters situation cannot be avoided by these means, the vessel must reduce speed to the minimum at which she can be kept on her course — and, if necessary, take all way off — navigating with extreme caution until the danger of collision has passed.

Lights and shapes tell the other vessel — and the examiner — what you are, without a word being exchanged. A power-driven vessel underway shows a masthead light over an arc of 225° (from right ahead to 22.5° abaft the beam on each side), sidelights over 112.5° each side from right ahead — green to starboard, red to port — and a sternlight over the remaining 135° arc astern. The sidelights and sternlight between them account for the full 360° of the horizon in colour, with no gap and no overlap, while the white masthead light's 225° arc sits over the same forward sector as the two sidelights. All-round lights — used for anchor lights and many status lights such as not-under-command or restricted-in-ability-to-manoeuvre — are, by definition, visible over the whole 360°. A vessel towing, where the length of the tow exceeds 200 metres, shows a third masthead light in a vertical line and, by day, a diamond shape where it can best be seen; that extra light is often the only clue, at a distance, that the tow is unusually long. Examiners mark on the exact arrangement — number, colour, arc and relative position of each light — not a paraphrase of "she showed the usual lights."

Sound signals under Rule 34 are manoeuvring and warning signals used when vessels are in sight of one another: one short blast means "I am altering course to starboard," two short blasts "to port," three short blasts "I am operating astern propulsion," and five or more short blasts is the doubt or danger signal, sounded whenever the other vessel's intentions or actions are not understood, or when it is doubted that sufficient action is being taken to avoid collision. In restricted visibility, Rule 35 uses a different vocabulary built on prolonged blasts: a power-driven vessel making way sounds one prolonged blast at intervals not exceeding two minutes; underway but stopped and making no way, two prolonged blasts in succession at the same interval. A vessel at anchor rings her bell rapidly for about five seconds at intervals not exceeding one minute, rather than sounding her whistle at all. The two sets of signals are not interchangeable, and using the wrong one for the visibility condition is itself a Rule 2 failure.

The two scenarios below are the kind an oral examiner builds from a single radar plot or a single light configuration, then keeps layering complications onto until the candidate's reasoning, not just their recall, is exposed.