An Isolated Danger Mark, as defined by the International Association of Lighthouse Authorities

International Association of Lighthouse Authorities

The International Association of Marine Aids to Navigation and Lighthouse Authorities is a non-profit organization founded in 1957 to collect and provide nautical expertise and advice.-Background:...

, is a sea mark

Sea mark

A sea mark, also seamark and navigation mark, is a form of aid to navigation and pilotage aid which identifies the approximate position of a maritime channel, hazard and administrative area to allow boats, ships and seaplanes to navigate safely....

 used in maritime pilotage

Pilotage

Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination, sometimes with the help of a map or nautical chart. People use pilotage for activities such as guiding vessels and aircraft, hiking and Scuba diving...

 to indicate a hazard to shipping such as a partially submerged rock.
It is recognisable by its black and red bands and top-mark of two black balls.

it`s distinctive sequence of flashing light consists of 2 quick flashes with intervals of 5 seconds.

See also

• Navigation
  Navigation
  Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
  
  
• Lateral mark
  Lateral mark
  A lateral buoy, lateral post or lateral mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the edge of a channel....
  
  
• Cardinal mark
  Cardinal mark
  A cardinal mark is a sea mark used in maritime pilotage to indicate the position of a hazard and the direction of safe water....
  
  
• Safe water mark
  Safe water mark
  thumb|right|Examples of Safe Water MarksA Safe Water Mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the end of a channel...
  
  
• Special mark
  Special mark
  A Special Mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the boundary of an obstruction, administrative area such as a speed limit, water skiing or mooring area, or to highlight other features such as outfall sewerage...