Module 15 - Restricted Visibility
Precautions in Fog
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 |
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 19 August 2026 - Day Skipper Revision.
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