A while back I attended a lecture at our local library given by a diver who is involved in the search for the shell that is believed to be the first shot fired after World War One was declared.
On August 5th 1914 a German merchant vessel the SS Pfalz, was intending to leave port before the declaration of war was made known. Britain had declared war on Germany as of 11pm on August 4th, which was 9am August 5th in Australia. As the ship reached Port Phillip Heads she ignored the signal to heave to. Upon orders from Fort Queenscliff a warning shot was fired across the bow from Fort Nepean. It was 12:45pm. The ship was returned to Melbourne under guard. She was later refitted for use by the allies during the war.