Module 15 - Restricted Visibility
Precautions in Fog
What you will learn
Carry out a coordinated restricted-visibility response without allowing position fixing or equipment set-up to displace safe speed, lookout and collision prevention.
There is no universal first action after visibility closes. The response must control speed, lookout, manoeuvring, lights, sound signals and navigation together, with tasks shared where the crew allows.
Proceed at a safe speed adapted to the circumstances and conditions, and review it continuously as visibility, traffic, sea room, wind, sea state and the yacht's manoeuvrability change. Safe speed is not a fixed number. It must leave enough time and distance to detect risk, assess it properly, take effective action and stop within an appropriate distance. A power-driven vessel must have her engines ready for immediate manoeuvre.
Maintain a proper lookout by sight and hearing as well as all available means appropriate to the conditions. Put a competent extra lookout where that person can see and hear effectively without being exposed to avoidable danger, reduce noise and distractions, and agree a simple reporting method. Exhibit the prescribed navigation lights in restricted visibility by day as well as night and make the correct Rule 35 sound signal in or near the affected area.
If circumstances allow, obtain and record a useful position while visual information remains, then continue monitoring position and depth with appropriate independent evidence. That task is part of the response, not a reason to delay safe speed, lookout, lights or signals. Brief the crew, secure loose equipment and use lifejackets, safety lines or other personal precautions according to the yacht, deck work and conditions; those seamanship choices do not replace the COLREG duties.
| Control | Immediate purpose | Important boundary |
|---|---|---|
| Safe speed | Preserve detection, assessment, manoeuvring and stopping time | Continuously review it; there is no universal number |
| Lookout | Build the best possible picture by sight, hearing and appropriate available means | No instrument or crew position substitutes for the full Rule 5 duty |
| Lights and signals | Make vessel status detectable and recognisable | Exhibit and sound the prescribed signals; do not assume they have been seen or heard |
| Position and depth | Keep the yacht in safe water and expose conflicts in the evidence | A single electronic source or depth reading is not a complete fix |
Share a sudden-visibility response
A three-person yacht under power enters a fog bank on a coastal leg. One person is helming, one is below checking the plot and one is resting. A fishing-vessel signal may be heard ahead.
1. Control
Bring the vessel to a continuously reviewed safe speed and keep the engine ready for immediate manoeuvre.
2. Detect
Call the rested crew member, post an effective extra lookout and protect hearing from avoidable cockpit and cabin noise.
3. Be detected
Exhibit navigation lights and start the correct power-driven-vessel sound signal at the required interval.
4. Navigate
Record the best available starting position if circumstances allow, then compare GNSS, depth, chart, radar if fitted and the planned safe-water limits.
5. Reappraise
Treat the possible signal ahead as a collision-risk warning and apply the Rule 19 response rather than pressing on to regain the schedule.
Sense check: If everyone is looking at the chart or radar, the yacht has not maintained the sight-and-hearing lookout required by Rule 5.
Common mistake or limitation
- Teaching 'get a fix first' as a universal order; the response is coordinated and collision-prevention duties cannot wait for a plotted position.
- Choosing one reduced speed and leaving it unchanged even as traffic, sea room, visibility or the ability to assess targets changes.
- Sending an extra lookout to an exposed bow without balancing hearing, communication, cold, spray and personal safety.
- Assuming navigation lights or a radar reflector guarantee that a larger vessel will detect the yacht in time.
Recap
- Restricted visibility needs a coordinated response, not one universal first task.
- Safe speed and lookout are continuing judgements, while lights, signals and engine readiness support detection and manoeuvre.
- Position evidence matters, but it never replaces collision prevention or a safe route.
Optional quick check
Section 2 of 5
Visibility closes while a yacht is under power. Which instruction is the best starting brief?
Sources and factual review
Reviewed 1 September 2026 - Day Skipper Revision.
Continue studying Restricted Visibility
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