Navigating in fog and restricted visibility (Rule 19)
Navigation Rules, lights & bridges · Power & sail
When vessels can't see each other in or near fog, mist, snow or heavy rain, Rule 19 replaces the give-way and stand-on rules. Every vessel must go at a safe speed for the visibility, keep engines ready, avoid close quarters, and slow right down when it hears a fog signal ahead of the beam.
Commonly missed
- There are no stand-on vessels in fog. Rules 11-18 apply only once you can see the other vessel, so don't assume a sailboat or fishing boat has priority you can rely on when neither of you can see the other.
When Rule 19 applies
- It applies to vessels not in sight of one another when navigating in or near an area of restricted visibility: fog, mist, falling snow, heavy rainstorms, sandstorms and similar causes (Rule 19(a), Rule 3(l)).
- Vessels are in sight of one another only when one can be seen visually from the other. A target you see only on radar is not 'in sight' (Rule 3(k)).
Speed and readiness
- Proceed at a safe speed adapted to the visibility. A power-driven vessel keeps her engines ready for immediate maneuver (Rule 19(b)).
- Apply the lookout, safe-speed and avoidance rules with the poor visibility in mind, and sound the Rule 35 fog signals (Rule 19(c), Rule 35).
Contacts seen only on radar
- If radar alone shows another vessel, decide whether a close-quarters situation or risk of collision is developing. If so, act in ample time (Rule 19(d)).
- If you change course, as far as possible avoid turning to port for a vessel forward of the beam (unless you are overtaking it), and avoid turning toward a vessel abeam or abaft the beam (Rule 19(d)(i), (ii)).
Hearing a fog signal ahead
- Unless you have established there is no risk of collision: if you hear a fog signal apparently forward of the beam, or can't avoid close quarters with a vessel forward of the beam, slow to the least speed that keeps you on course (Rule 19(e)).
- Take all way off if necessary, and navigate with extreme caution until the danger of collision is over (Rule 19(e)).
The rules: COLREGS Rule 3 · COLREGS Rule 19 · 33 CFR 83.03 · 33 CFR 83.19 · COLREGS Rule 35
Sources (3)
A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.