Emily is the great great granddaughter of Captain Bernard Hindmarsh, who was one of the 268 people who lost their lives when a Japanese torpedo sent the converted passenger cargo vessel to the bottom off North Stradbroke Island on May 14, 1943.

''I was nervous but I felt proud [of my great great grandfather] as well.''

Her mother Tiffany was also proud on Tuesday, especially of her daughter, who spoke about what the death of Captain Hindmarsh had meant to his family and his community.

''I am incredibly proud of Emily and the fact she had the nerve to do this; she is taking the memories of the Centaur forward to another generation.''

Emily told the gathering her great great grandfather had been a popular and respected doctor at Macksville on the mid north coast of NSW before the war. ''His friends called him 'Bertie', his patients called him 'Doc','' she said. ''When he joined the army they called him captain.''

Like the other members of the ship's medical team, Captain Hindmarsh's job was to save lives, not to take them.

The ship ferried wounded from the Kokoda Track back to Australia for treatment and, on her previous voyage, had transported wounded Japanese as well as Australians.

Crewed by merchant seamen, completely unarmed, painted white, marked with multiple red crosses and floodlit at night, Centaur should have been exempt from enemy action under the rules of war - including treaties to which Japan was a signatory.

That did not prevent Hajime Nakagawa, the commander of the Japanese submarine I-177, from firing at least one torpedo at the Centaur in the early hours of the morning of May 14.

The torpedo exploded at 4.10am, igniting the port side oil tank and setting the ship ablaze from the bridge to the stern. Within minutes she had sunk in 2000 metres of water and was not rediscovered until 2009.

Only 64 of the 332 people on board survived, and each of the deaths was a personal tragedy that resonated around the nation.

Emily said the citizens of Macksville were shocked to learn of their doctor's death while on a mission of mercy and established the Hindmarsh Gardens in his honour. ''The storyboard at the memorial says that Australia lost a patriotic citizen, the community lost a dedicated doctor and that a young family had lost a father,'' she said. ''If you multiply that by 268 times you will get a sense of what this meant.''

Bertie's widow Elma was left with three children to raise. Emily's great grandmother Elma was one of them. Only six at the time of the tragedy, she could not accept that her father was dead and spent years waiting for him to come home.

Later she played a key role in establishing the Centaur Association and campaigning for a search to locate the wreck. On December 20, 2009 it was found.