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Aids to navigationQuestion 257 of 352

Which light does an isolated danger mark show?

  1. A green light with one flash
  2. A white light with groups of two flashes
  3. A yellow fixed light
  4. A red light with Morse A
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Correct answer: A white light with groups of two flashes

The white group flashing two rhythm marks a danger you can pass on all sides.

Source: US Code of Federal Regulations (eCFR), 33 CFR Part 62: United States Aids to Navigation System, § 62.45 Light characteristics

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Questions last reviewed: 18 October 2026