Boating Coach US
Aids to navigationQuestion 233 of 352

Which topmark does an isolated danger mark carry?

  1. One red sphere
  2. Two red cones
  3. One black diamond
  4. Two black spheres, one above the other
Show answer

Correct answer: Two black spheres, one above the other

The mark is black with red bands. The two black balls tell you it sits on or near a danger.

Source: US Code of Federal Regulations (eCFR), 33 CFR Part 62: United States Aids to Navigation System, § 62.29 Isolated danger marks

All questionsPractice the topic "Aids to navigation"

Questions last reviewed: 18 October 2026