Module 15 - Restricted Visibility
Systematic Fog Strategy
What you will learn
Build and command a vessel-specific restricted-visibility playbook with entry triggers, task ownership, safe-water choices and an anchoring boundary.
A useful strategy is not a memorised eight-step script. It is a prepared control loop that keeps the Rules, route, equipment and crew aligned as the picture changes.
Before entry, identify the visibility trigger, traffic and hazard exposure, safe speed considerations, radar and sound-equipment set-up, crew call points, safe water and the last usable diversion or anchorage. Practise the equipment in clear conditions. A response invented after orientation is lost is slower and more error-prone than one the crew has already briefed.
During the event, maintain a short repeated cycle: control speed and manoeuvring readiness; detect by sight, hearing and appropriate available means; be detectable with lights and correct sound signals; navigate with position, depth and route limits; assess every contact under the correct Rules; communicate a concise shared picture; and reappraise whether the route still has safe margin. Record material observations and decisions without pulling the whole crew away from lookout and control.
Anchoring can reduce exposure only when the yacht can reach and identify a suitable charted position clear of channels and traffic, with safe depth, holding, swinging room, weather and local permission. It does not remove collision risk or lookout duties. Never anchor merely because a shipping lane is nearby or because the position is uncertain. Once anchored, exhibit and sound the required signals and continue monitoring.
| Loop | Question | Command output |
|---|---|---|
| Control | Does speed preserve time, stopping and manoeuvre? | Reviewed speed and engine readiness |
| Detect | What can sight, hearing, radar and other means establish? | Shared contacts, uncertainty and blind sectors |
| Be detected | Are the correct status signals being shown and sounded? | Lights, sound interval and reflector boundary |
| Navigate | Is the yacht in safe water and does evidence agree? | Position, depth trend, route limit and alternative |
| Reappraise | Does the original route still retain margin? | Continue, hold, divert or anchor in a checked place |
Choose between continuing, holding and anchoring
The yacht is outside a harbour approach in worsening visibility. A charted anchorage lies clear of the channel, but reaching it requires crossing the inbound lane. Safe open water remains available offshore and the harbour entrance depends on visual transits.
1. Reject the attractive shortcut
Do not cross the inbound lane merely because the anchorage would stop the yacht's own movement.
2. Protect safe water
Use the offshore safe-water option while lookout, radar and route evidence can be sustained.
3. Reappraise the entrance
Delay the visual-transit pilotage until the required marks and traffic can be identified with margin.
4. Use an anchorage only if reachable safely
Check route, channel separation, position, depth, holding, swinging room, weather and local restrictions before committing.
Sense check: Stopping movement is not automatically safer when reaching the stopping place creates the greater traffic conflict.
Common mistake or limitation
- Using a rigid 'fix, slow, lights, horn' sequence as if later duties can wait for earlier tasks to finish.
- Monitoring every display continuously without allocating a human sight-and-hearing lookout or preserving a shared picture.
- Anchoring near a traffic lane or while uncertain of position on the assumption that anchoring removes collision risk.
- Resuming the original route as soon as visibility improves without re-establishing position, traffic, crew and pilotage margin.
Recap
- Prepare triggers, roles, equipment and alternatives before visibility closes.
- Run a repeated control, detection, signalling, navigation and reappraisal loop rather than a one-off sequence.
- Anchor only in a verified suitable place reached without creating the greater risk.
Optional quick check
Section 8 of 8
A charted anchorage requires crossing an inbound lane while safe open water remains offshore. What is the stronger fog contingency?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
Continue studying Restricted Visibility
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