Special mark

A Special Mark, as defined by the International Association of Lighthouse Authorities, is a sea mark used in maritime pilotage.

It is recognisable by its yellow colour and X, (also referred to as a St. Andrews Cross or saltire) top-mark.

It has a distinctive sequence of various flashes that does not match any other navigational mark flashes in its vicinity.

Special marks can indicate:

Examples of Special Marks
A Special mark indicating an outfall pipe in the Irish Sea off Helen's Bay , Northern Ireland . It has the flashing sequence Fl.(2).Y meaning it flashes yellow twice, this is called group flashing.