Rule 34(d) · Maneuvering & warning
Danger / doubt signal
At least five short and rapid blasts: “I doubt your intentions — or I see danger.” The most important signal to recognize instantly.
You hear: 5 short blasts.
Meaning
When vessels in sight are approaching and one fails to understand the intentions or actions of the other, or doubts whether sufficient action is being taken to avoid collision, she sounds at least five short and rapid blasts on the whistle. May be supplemented by at least five short and rapid light flashes.
Also the mandatory reply to a passing proposal you disagree with: if you doubt the safety of a proposed maneuver, sound the danger signal and take precautionary action until an agreement is reached.
Key facts
- Sounded by
- Any vessel in sight of another that doubts the other's intentions or actions
- Repeated
- Not a repeating signal — sounded when the situation calls for it
- Applies under
- International & US Inland
- Notation
- · · · · ·
Related signals
Source: Rule 34(d) — USCG Navigation Rules (International & Inland)
Rule text is reproduced from the public-domain USCG Navigation Rules. Audio is synthesized to Rule 32 timings.