HMAS Sydney was an Australian warship that was lost in a battle with a German ship in the Indian Ocean in World War 2.
Both ships sunk without a trace – all 645 men on board the HMAS Sydney died. The HMAS  Sydney and the German vessel were both found in 2008 off the coast of Freemantle in WA.
There are other HMAS warships like the HMAS Melbourne that fought alongside HMAS Sydney.
There is a museum here in Sydney that shows the ruins of the great ship with these words that most people shall know:
Lest we Forget.

PS: HMAS stands for “Her Majesty’s Australian Service” and every naval ship has this in front of the name of the ship.

By Evan 

Image: ‘HMAS Sydney‘ ,  ‘HMAS Sydney‘,