Module 16 - Pilotage
Other Marks
What you will learn
Distinguish isolated danger, safe water, special and emergency-wreck marks and connect each family to the correct cautious action.
These marks can look superficially similar while sending very different messages. The skipper must distinguish a hazard at the mark from navigable water, a chart-defined special feature and a newly reported danger.
An isolated danger mark is black with one or more broad red horizontal bands, carries two black spheres when fitted and shows white Fl(2) when lit. It is placed on or near a danger with navigable water around it, but that does not invite a close pass: the chart establishes the hazard and a prudent clearance.
A safe water mark has red-and-white vertical stripes, may carry one red sphere and, when lit, uses a white isophase, occulting, one long flash every 10 seconds or Morse A characteristic. It may serve as a fairway, mid-channel or landfall mark. 'Safe water' still requires the normal depth, traffic and route checks.
A special mark is yellow, may carry a yellow X and uses a yellow light whose rhythm does not conflict with another mark family. It identifies a special area or feature; the chart or local notice supplies the meaning. An emergency wreck marking buoy instead uses blue-and-yellow vertical stripes and, when lit, alternating blue and yellow to warn of a new danger.
Two spheres and two white flashes reinforce the danger-at-the-mark message.
| Mark | Day cues | Light if fitted | Immediate interpretation |
|---|---|---|---|
| Isolated danger | Black/red bands; two black spheres | White Fl(2) | Danger at or near the mark |
| Safe water | Red/white vertical stripes; one red sphere | White Iso, Oc, LFl.10s or Mo(A) | Navigable water around the mark |
| Special | Yellow; yellow X if fitted | Yellow, non-conflicting rhythm | Chart-defined area or feature |
| Emergency wreck | Blue/yellow vertical stripes | Alternating blue/yellow | New danger requiring caution and updates |
Do not turn a safe-water cue into a guarantee
After a night landfall the crew identifies a white Morse A light at the charted fairway position and proposes steering directly beside it at full speed.
1. Confirm the family
Morse A is one permitted safe-water characteristic; compare position and any visible red/white vertical body.
2. Read the limited message
Navigable water exists around the mark, but the mark does not promise uniform depth or absence of traffic.
3. Use the plan
Take the charted fairway track with the planned speed, depth checks, lookout and clearance from the buoy.
Sense check: A safe-water mark supports a route; it does not cancel the echo sounder, chart, traffic picture or uncertainty in the buoy's position.
Common mistake or limitation
- Isolated danger and safe water both mention navigable water around a mark, but one warns of a hazard at the mark and the other marks useful water.
- A yellow special mark has no universal pass side; its local meaning must be read from the chart or notice.
Recap
- Use band direction, topmark and light rhythm to separate these families.
- Translate each name into its limited message before choosing a route.
- Check the chart, current notices, depth and traffic even after correct recognition.
Optional quick check
Section 8 of 8
What is the essential difference between an isolated danger mark and a safe water mark?
Continue studying Pilotage
This public lesson is part of Revision Module 16. Full revision access adds the guided Learn, Practise and Test flow, flashcards and revision progress.