Rule 5: why look-out is the rule examiners care about most

Ask an examiner which rule features in more incident reports than any other and the answer is usually the shortest rule in the book. Rule 5 is two sentences long, and it underpins everything else.

What the rule says

Rule 5 requires that 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.

Four phrases carry the weight:

• At all times - underway, making way or not. There is no condition in which the duty lapses.
• By sight and hearing - the rule explicitly names human senses. Radar and AIS supplement them; they do not replace them. A sound signal heard in fog is look-out information.
• All available means - if you have radar and conditions warrant it, you are expected to use it. "We had radar but it was off" reads very badly in an incident report.
• Full appraisal - look-out is not just detection. It is understanding what you are seeing: aspect, change of bearing, risk of collision.

Why it matters beyond the exam

Rule 5 is the foundation that Rules 6 (safe speed), 7 (risk of collision) and 8 (action to avoid collision) build on. You cannot judge a safe speed for conditions you have not appraised, and you cannot assess risk of collision on traffic you have not seen. That chain is why collision investigations so often start with the look-out question.

For short-handed crews the practical questions are real: who is watching while you reef? While you are at the chart table? A proper look-out is a matter of organisation, not just eyesight.

How it shows up in exams

Expect scenario questions rather than recitation: restricted visibility with a fog signal heard forward of the beam, a single-hander using autopilot, a motor cruiser relying on AIS alone. The examiner is testing whether you understand that "all available means" includes ears, eyes, radar and plotting - used together, appropriate to conditions.

The IRPCS app drills Rule 5 in context: scenario questions cite the rule in every explanation, and the weak-spots drill resurfaces it until your accuracy holds.

FAQ

Does Rule 5 apply at anchor? The rule says "every vessel" and "at all times". Anchored vessels have been found at fault for failing to keep a look-out - an anchor watch in appropriate conditions is good seamanship and widely treated as required.

Is AIS an acceptable look-out on its own? No. AIS is one of the "available means" - not all vessels transmit, and the rule explicitly requires sight and hearing.

Is Rule 5 different in US Inland waters? Inland Rule 5 mirrors the International rule - the look-out duty is the same.