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COLREG

Rule 36: Signals to Attract Attention

To attract attention, avoid strobe lights while keeping signals clear and vessels unembarrassed.

Rule 36 of 41

Decide

Decision 1 of 2

You want to attract another vessel's attention and think of giving this signal. Is it right?

The rule in plain words

  1. What may you do?Any vessel may make light or sound signals to attract attention, but they must not be mistaken for authorised signals elsewhere in the Rules.
  2. What about the searchlight?You may direct the beam of your searchlight in the direction of the danger, but do so without embarrassing any vessel.
  3. What light is suitable?Any light used to attract attention must not be mistaken for an aid to navigation; avoid high intensity intermittent or revolving lights, such as strobe lights.
An attention signal must not be mistaken for another prescribed signal. A searchlight may indicate danger without dazzling or confusing another vessel; required navigation lights remain displayed.

Before you read on: what would you do?

Question 1/1

If you need to attract another vessel's attention, what does Rule 36 allow?

Listen to it

Play each signal and listen: this is how it sounds at sea.

Frequent mistakes

  • Wrong: "Any signal is acceptable if the other vessel sees it."

    Right: The signal must not be mistaken for any signal authorised elsewhere in the Rules.

  • Wrong: "I may sweep the searchlight across nearby vessels."

    Right: Direct the beam towards the danger without embarrassing any vessel.

  • Wrong: "A strobe light is ideal for attracting attention."

    Right: Avoid high intensity intermittent or revolving lights, such as strobe lights.

Exam keys & interpretation

  1. "Any vessel" does not mean any signal: it must not be mistaken for an authorised signal.
  2. "Direction of the danger" permits the searchlight; "without embarrassing" remains a condition.
  3. "High intensity intermittent or revolving" points to lights to avoid, with strobe lights as the example.

How to read it

Read "may" as an option to attract attention, not permission to use a signal that resembles an authorised one.

The searchlight can indicate the danger, but the method must not embarrass any vessel.

Key points

  • Light or sound signal → never mistaken for a signal authorised elsewhere in the Rules.
  • Searchlight beam → direction of the danger · no vessel embarrassed.
  • Attention light → distinct from every aid to navigation.
  • High intensity + intermittent/revolving → avoid; strobe lights are the example.

Test your knowledge

3 questions to check it. Pick an answer to see why.

Question 1/3

How may the searchlight be used to attract attention?

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Official text

IMO COLREG 1972 U.S. Coast Guard — International Navigation Rules (2024)

Full wording of the rule, reproduced from the official source below.

If necessary to attract the attention of another vessel, any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel. Any light to attract the attention of another vessel shall be such that it cannot be mistaken for any aid to navigation. For the purpose of this Rule the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided.
Source:

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Reviewed by Ramon Curto, Nautical teacher at IECNPC · Last reviewed:

Frequently asked questions about COLREG Rule 36

What signals may a vessel use to attract attention?

Necessary light or sound signals that cannot be mistaken for a COLREG signal or an aid to navigation (Rule 36). A searchlight directed toward danger must not embarrass another vessel, and high-intensity intermittent or revolving lights, such as strobes, should be avoided.

Can a searchlight be used under COLREG Rule 36?

Yes — a searchlight may be directed towards a danger to attract attention, as long as the signal cannot be mistaken for a prescribed signal or an aid to navigation.

Which attention-getting signals are not allowed?

Any signal that could be mistaken for one authorized elsewhere in these Rules or for an aid to navigation. Using something that could be confused with a distress signal is the common mistake.