Fog, underway, International and Inland
Power vessel making way
Power-driven and moving through the water.
One prolonged blast
Who sounds it
Power-driven vessel making way through the water.
How it's sounded
Prolonged blast: 4 to 6 seconds (Rule 32(c)); 5 seconds is used here.
At intervals of not more than 2 minutes.
A short blast is about 1 second. A prolonged blast is 4 to 6 seconds. Clips use 1 and 5 seconds.
In or near an area of restricted visibility, by day or by night. You don't have to be inside the fog.
Worth remembering
One long, on the move.
The same sound elsewhere
These use the same pattern, so the rules you’re under and the situation decide what it means.
More in fog, underway
- Power vessel stoppedInternational and Inlandtwo prolonged blasts
- Limited vessels, underwayInternationalone prolonged blast, then two short blasts
- Limited vessels, underwayInlandone prolonged blast, then two short blasts
- Fishing or restricted, at anchorInternationalone prolonged blast, then two short blasts
- Fishing or restricted, at anchorInlandone prolonged blast, then two short blasts
- Vessel being towedInternational and Inlandone prolonged blast, then three short blasts
- Composite unit stoppedInternational and Inlandtwo prolonged blasts
- Pilot vessel identityInternational and Inlandfour short blasts
Study more
See every sound signal, try the free Rules of the Road practice test, or read who gives way, and how Inland differs.
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