Isolated danger marks

An isolated danger mark stands on or near a danger with navigable water around it. This relates the mark to a localised danger rather than making its immediate vicinity clear water. R1001 explicitly explains that danger extent and safe passing distance cannot be specified for every use of this mark. The drawing separates the aid, a fictional danger and information still needed about the area. It supplies neither a safety circle nor a route to follow. The name identifies a category, not a measurement of the hazard’s outline.

The body is black with one or more broad red horizontal bands. Shape must not conflict with laterals; pillar and spar are usual forms. The topmark comprises two black balls vertically, clearly separated: balls rather than cones. That helps distinguish isolated danger from cardinals, which also have black upper elements but different geometry. Body colour and topmark form can be observed at different moments, and one can be obscured by waves, viewing angle or backlighting. An unreadable component leaves evidence incomplete rather than changing the definition.