Warnings, International and Inland
Nearing a bend
A warning to vessels that may be hidden around a bend or behind an obstruction.
One prolonged blast
Who sounds it
Any vessel nearing a bend or an area of a channel or fairway where others may be obscured.
How it's sounded
Prolonged blast: 4 to 6 seconds (Rule 32(c)); 5 seconds is used here.
A short blast is about 1 second. A prolonged blast is 4 to 6 seconds. Clips use 1 and 5 seconds.
Worth remembering
It doesn't replace passing signals. Those still apply once vessels are in sight.
The same sound elsewhere
These use the same pattern, so the rules you’re under and the situation decide what it means.
More in warnings
Study more
See every sound signal, try the free Rules of the Road practice test, or read who gives way, and how Inland differs.
Learn the whole set
Helm drills every signal with flashcards and spaced review, on the web and iPhone.
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Helm is an independent study aid, not affiliated with or endorsed by the U.S. Coast Guard or the National Maritime Center. This page is for study, not navigation guidance or legal advice. Check the current rules before you rely on anything here.