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IALA A Buoyage revision module 4 of 5

MARK

Danger, Safe Water, Special, and Emergency Wreck Marks

Isolated danger, safe water, special marks, and emergency wreck marking with recognition cues and light rhythms.

isolated dangersafe water

8 guided lessons · 10 practice questions · 10 flashcards

3 outcomes · self-guided revision
  • Distinguish isolated-danger, safe-water, special and emergency-wreck marks by the navigation question each family answers before using colour, topmark or light detail.
  • Explain why navigable water around both families does not make isolated danger and safe water interchangeable, then state the different route checks each requires.
  • Combine the isolated-danger body's horizontal black and red bands, two-sphere topmark, white group-flashing-two light and charted position without inventing a fixed body shape or passing distance.

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Lesson previewFour Other-Mark Families, Four Different Messages1 section shown

Preview lesson

Four Other-Mark Families, Four Different Messages

Begin with family rather than a memorised side to pass. An isolated-danger mark is placed on, moored on or above a local danger with navigable water around it. A safe-water mark states that navigable water exists all around and may be used for a fairway, centre line, mid-channel position, approach or landfall.

A special mark indicates a special area or feature whose nature is found in the chart or another nautical publication. It is not normally used for a channel or obstruction when another IALA family is more suitable. An emergency-wreck buoy instead gives conspicuous temporary warning of a newly marked wreck or danger while information and permanent marking develop.

The family changes the next question. Isolated danger requires the danger's extent and a safe passing distance. Safe water requires confirmation that the charted route, depth and traffic suit this vessel. Special requires the local purpose, boundary or restriction. Emergency wreck requires current warnings, the marked pattern and a conservative route clear of an incompletely surveyed hazard.

Colour alone is insufficient. Black can combine with red or yellow, yellow can mean special, cardinal or part of an emergency-wreck pattern, and white lights serve several families. Combine body pattern, permitted shape, topmark, complete light, charted position and current information before acting.

Family identity changes the decision: avoid a local danger, interpret navigable water, investigate a special purpose or protect the vessel from a newly marked wreck.

FamilyQuestion it answersImmediate follow-up
Isolated dangerWhere is a small local danger with navigable water around it?Find its extent and a safe passing distance from current information
Safe waterWhere is navigable water all around this aid?Confirm the route, depth, traffic and vessel margin
SpecialWhat special area or feature is charted here?Read the symbol, notes, notice, lettering or authorised pictogram
Emergency wreckWhere is a newly marked wreck or danger?Use current warnings and keep a conservative distance from the marked pattern

Optional quick check

Section 1 of 1

A crew member reports only 'yellow buoy ahead'. What is the best first response?

Choose one answer
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