Warnings, International and Inland

Attracting attention

Any light or sound signal that can't be mistaken for a signal authorized in the Rules, or a searchlight directed at the danger, without embarrassing any vessel.

Who sounds it

Any vessel, if necessary.

How it's sounded

No fixed pattern. Whatever is used must not be mistakable for a signal in the Rules.

A short blast is about 1 second. A prolonged blast is 4 to 6 seconds. Clips use 1 and 5 seconds.

Worth remembering

The rule sets no fixed sound. Under International rules, the light must not be mistaken for an aid to navigation, and strobes are to be avoided.

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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Sources

Rule 36; Inland Rule 36, 33 CFR 83.36

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.