COLREGS PrepDownload the iOS app

Rule 36: Signals to Attract Attention (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 36 lets any vessel use light or sound signals to attract attention, as long as they can't be mistaken for any signal authorized elsewhere in the rules, or direct a searchlight toward the danger without embarrassing any vessel. International adds that strobe-type lights should be avoided.

The rule text

may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 36

For the purpose of this Rule the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 36

What it means on the water

  • Any vessel may use a light or sound signal to attract attention.
  • It must not be mistakable for another authorized signal.
  • A searchlight may be pointed toward the danger, not into another vessel's bridge.

International vs Inland

International adds two sentences: any attention light must not be mistakable for an aid to navigation, and high intensity intermittent or revolving lights such as strobes shall be avoided. Inland Rule 36 doesn't include them.

Common exam traps

  • Using five short blasts to attract attention. That's the Rule 34(d) doubt signal.
  • Using a strobe in International waters.

Try 3 questions on Rule 36

  1. Rule 36 signals must not be:

    1. Loud
    2. Mistaken for any signal authorized elsewhere in the rules
    3. Used at night
    4. Used Inland
    Show answer

    B. Mistaken for any signal authorized elsewhere in the rules Rule 36.

  2. International Rule 36 says to avoid:

    1. Searchlights
    2. Strobe lights
    3. Whistles
    4. Bells
    Show answer

    B. Strobe lights International Rule 36.

  3. Where may a searchlight be directed?

    1. At the other vessel's bridge
    2. In the direction of the danger, without embarrassing any vessel
    3. Straight up
    4. Anywhere
    Show answer

    B. In the direction of the danger, without embarrassing any vessel Rule 36.

Frequently asked questions

Can I use a strobe to get attention?

International Rule 36 says high intensity intermittent or revolving lights, such as strobes, shall be avoided.

Can I use a searchlight?

Yes, directed toward the danger in a way that doesn't embarrass any vessel.

Inland difference?

Inland omits the aid-to-navigation and strobe sentences.

Related rules and guides