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What do five or more short, rapid blasts on a boat's horn mean?

Doubt about the other boat's intentions or actions.

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  1. Doubt about the other boat's intentions ✔
  2. I'm leaving the dock
  3. All clear, go ahead

Why: Inland Rule 34(d) says a vessel that doesn't understand another's intentions, or doubts it's doing enough to avoid collision, must immediately sound at least five short, rapid blasts.

Huh, didn't know that: The five-blast signal may be backed up with at least five short, rapid flashes of light.

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References

Answer: Doubt about the other boat's intentions. Inland Rule 34(d) says a vessel that doesn't understand another's intentions, or doubts it's doing enough to avoid collision, must immediately sound at least five short, rapid blasts.

  1. 33 CFR 83.34 Maneuvering and warning signals, Inland Rule 34 (eCFR) www.ecfr.gov/current/title-33/section-83.34
    the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle.
    Checked 2026-10-08.

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