Module 15 - Restricted Visibility
Precautions in Fog
What you will learn
Command a coordinated restricted-visibility response without letting position fixing or equipment set-up displace safe speed, lookout, lights, signals and manoeuvring readiness.
There is no universal first action. Control, detection, signalling, navigation and crew safety have to be organised together, then reviewed as conditions change.
Every vessel must proceed at a safe speed adapted to the circumstances and conditions. It is not a fixed number or simply 'minimum steerage way': it must preserve time and distance for detection, full appraisal, effective avoiding action and stopping within an appropriate distance. Review it continuously as visibility, traffic, sea room, wind, sea and manoeuvrability change. A power-driven vessel must have its engines ready for immediate manoeuvre.
Maintain a proper lookout by sight and hearing as well as every available means appropriate to the conditions. Add a competent lookout when workload requires, but choose a position that supports sight, hearing and communication without exposing the person unnecessarily. Reduce avoidable noise and agree a short reporting format. Exhibit the prescribed navigation lights in restricted visibility by day and night, and make the vessel-status sound signal in or near the affected area.
If circumstances allow, obtain and record a useful starting position while visual information remains, then keep position and depth under review. That task is part of the response, not a reason to delay speed reduction, lookout, lights, sound signals or engine readiness. Share tasks, call rested or more experienced crew early and keep the skipper's cognitive load below the point where a growing traffic picture can no longer be understood.
| Control | Purpose | Boundary |
|---|---|---|
| Safe speed | Preserve assessment, manoeuvring and stopping time | Continuously reviewed; no universal figure |
| Lookout | Build the best picture by sight, hearing and appropriate available means | No fixed crew position or instrument completes Rule 5 alone |
| Lights and signals | Make vessel status detectable and recognisable | Do not assume they have been seen, heard or located accurately |
| Position and depth | Keep the yacht in safe water and expose conflicting evidence | One GNSS position or depth is not independent confirmation |
Brief the first minute without a false sequence
A yacht under power enters a fog bank with four people aboard. One is helming, one is navigating below, one is inexperienced and one is resting. A sound signal may be heard ahead.
1. Control
Set and keep reviewing a safe speed; confirm the engine is ready for immediate manoeuvre.
2. Detect
Call the resting crew member, establish a protected sight-and-hearing lookout and reduce avoidable noise.
3. Be detected
Exhibit the correct lights and begin the prescribed sound signal for the yacht's actual status.
4. Navigate
Record useful position evidence if circumstances allow and compare chart, depth, GNSS and radar without treating any one source as confirmation.
5. Reappraise
Apply the Rule 19 response to the apparent signal ahead and protect a safe-water or diversion option.
Sense check: If the helm, navigator and extra crew are all looking at one display, the yacht has not created the proper lookout or shared traffic picture it needs.
Common mistake or limitation
- Teaching 'get a fix first' as an absolute order; collision-prevention duties cannot wait for a plotted position.
- Reducing to one remembered speed and leaving it unchanged while traffic, sea room, visibility or manoeuvrability changes.
- Posting a lookout on an exposed bow without considering hearing, cold, spray, communication and personal safety.
- Assuming lights, sound signals or a radar reflector guarantee timely detection by another vessel.
Recap
- Restricted visibility needs a coordinated response rather than one universal first task.
- Safe speed and lookout are continuous judgements; lights, signals and engine readiness support detection and manoeuvre.
- Use the crew to reduce workload and preserve a shared, current traffic and navigation picture.
Optional quick check
Section 2 of 10
Visibility closes while a yacht is under power. Which brief is the strongest starting point?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
Continue studying Restricted Visibility
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