When exploring the National Archives of Australia for files relating to UAP, researchers have traditionally looked back only to the early 1950's. This is due to the fact that the Air Board/RAAF involvement can only be traced back that far.
Melbourne researcher Paul Dean has been checking files which stretch back as far as 1917. One he found, file series MP367/1 control symbol 512/3/200, bar code 355679 is titled "Suspicious lights at Port Kembla."
The 14 page file is the report of observations on Sunday, 14th October 1917, between 7 and 8 p.m. from number 4 jetty at Port Kembla. Stuart E Graham was on the jetty fishing, when he saw a stationary light to the West. It started to flash, almost went out and "...appeared to be carried in the direction of the old quarry...the light was set down and started flashing again..." 10 minutes later the light came back towards Port Kembla. It flashed for another 5 minutes. Mr Graham, for some reason, thought the flashing light was using morse code.
A number of other people were also on the jetty at the time. Francis Robert Williams made a statement advising that Grahm drew his attention to the light which appeared to be on land "...about the turn off from the Wollongong road to Unanderra." Williams also said he thought the light was using morse code.
At 2am on the 15th October 1917 Williams reported seeing the light again, flashing for 20 minutes in roughly the same direction as the light from the previous night. At about this time Williams believed he heard the whistle of a boat in the area and saw smoke coming from it.
An investigation was conducted by a Police inspector who concluded that neither Williams nor Graham knew anything of morse code. The gist of the investigation was to determine if someone was deliberately signalling from land to a passing boat. The inspector didn't believe this to be so.
The police report was forwarded to the Secretary, Department of Defence, Melbourne.
What was the light?
A good question! Based on the limited information which can be extracted from the file, it is not possible to arrive at any reasonable conclusion.
As a P.S. I did previously find a file which related how some mysterious lights on a hillside, in 1915, upon investigation turned out to be a troupe of boy scouts carrying lights.