BOATsmart! Base de connaissances du Canada 

An Isolated Danger Buoy is used to mark an isolated hazard or obstruction such as a rock, shoal or sunken island. This buoy will be moored on, or above, an isolated danger that has navigable (i.e. safe) water all around it. You should refer to a marine chart to determine the features of the isolated danger (i.e. size, depth, exact location etc.) and should navigate well clear of the marked danger.

Isolated Danger Buoys are identified by the following:

• They are black in colour with a wide red band at the midpoint
• They have a top-mark consisting of two black balls
• They may be equipped with a white light that flashes in a FL(2) sequence–a two flash sequence repeated every four seconds