Just as a note, in OZ the Alpha flag is the recognised dive flag too.
From Western Australian Department of Transport;
All vessels are required to display a flag of size 6 of the International Flag Code or not less than 750 mm in length and not less than 600 mm in width.
[h=3]Diving from a boat[/h]Any boat with divers operating from it must always display signals by day or night to inform other boat users.
The daytime signal for divers is an International Code Flag A. The flag must be at least 750mm long and 600mm wide.
[h=3]Diving without a vessel[/h]Divers operating without a vessel must also display the International code flag A.
The flag may be displayed from a jetty (for example) and must be at least 750mm long and 600mm wide.
Exception to size: If displayed from a buoy, the flag must not be less than 300 mm in length and 200 mm in width.
The flag must be clearly visible to all vessels operating in the vicinity.
From Western Australian Department of Transport;
All vessels are required to display a flag of size 6 of the International Flag Code or not less than 750 mm in length and not less than 600 mm in width.
[h=3]Diving from a boat[/h]Any boat with divers operating from it must always display signals by day or night to inform other boat users.
The daytime signal for divers is an International Code Flag A. The flag must be at least 750mm long and 600mm wide.
[h=3]Diving without a vessel[/h]Divers operating without a vessel must also display the International code flag A.
The flag may be displayed from a jetty (for example) and must be at least 750mm long and 600mm wide.
Exception to size: If displayed from a buoy, the flag must not be less than 300 mm in length and 200 mm in width.
The flag must be clearly visible to all vessels operating in the vicinity.