Module 15 of 17
Restricted Visibility
Precautions and limitations imposed by fog and restricted visibility.
Navigating in Fog
Fog is one of the most dangerous conditions for small-craft sailors. Visibility can drop to metres with little warning. Your ability to see hazards, other vessels, and navigation marks is severely reduced, and you may not be seen by others.
If fog is forecast, seriously consider whether the passage is necessary. If you are caught in fog at sea, take immediate precautions.
Key Points
- Fog can arrive suddenly with little warning
- Consider postponing passage if fog is forecast
- Take immediate action when visibility drops
Precautions in Fog
Fix your position immediately while you can still see landmarks. Switch on navigation lights. Start sounding fog signals (one prolonged blast every two minutes for a power vessel, one prolonged + two short blasts for a sailing vessel). Post extra look-outs — use eyes AND ears.
Reduce speed. Under Rule 6, every vessel must proceed at a safe speed adapted to the prevailing visibility. Have your radar reflector hoisted, and use radar or AIS if available. Put on lifejackets and consider clipping on harnesses.
Plot your position regularly using GPS. Monitor depth — your echo sounder is now a critical navigation tool. Consider anchoring if you are near shallow water and uncertain of your position.
Key Points
- Fix position while you still can see marks
- Navigation lights ON
- Sound fog signals (Rule 35)
- Post extra look-outs (sight AND hearing)
- Reduce speed to safe speed (Rule 6)
- Hoist radar reflector
- Put on lifejackets
- Monitor echo sounder continuously
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