Special mark
![Examples of Special Marks](/Images/godic/202502/12/IALA_specjal_mark4932.png")
![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.](/Images/godic/202502/12/Buoy_off_Seahill_-_geograph.org.uk_-_7208064932.jpg")
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, (often referred to as a St. Andrews Cross) top-mark. It has a distinctive sequence of various flashes that does not match any other navigational mark flashes in its vicinity.