Sydney Harbour's worst maritime disaster stopped the city in its tracks, and had a deep and lasting impact on the residents of Watsons Bay and Vaucluse.

Within seconds of the Greycliffe ferry from the City to Watsons Bay colliding with the passenger liner Tahiti on November 3, 1927, 40 people would die and many more would be injured. The afternoon trip - also known as the school boat - was packed with local residents who regularly commuted by ferry to work, school or studies.

Ken Horler, 90, is believed to be the only remaining survivor. His memory of the day is chillingly sharp. "It was 4.15 pm and we were just off Bradleys Head," Mr Horler said. "Everybody was sitting in their appointed spaces and I was outside at the stern on a seat with the other boys who always sat there. "There was no warning whatsoever and no evasive action. All of a sudden we were cut in half by the Tahiti's bow. We children were thrown overboard, and I was caught by a rope and taken down to such a great depth I thought I'd drown.

"I was able to release it and came up for breath but then the undertow took me down again. I finally made it back to the surface for air and found myself surrounded by the bobbing  heads, debris and drowning people." The then 14-year-old swam to a raft-sized piece of the ferry captain's cabin and helped others to climb onto it before other craft came to their rescue.

Incredibly, he and several others were taken by launch to the foreshore near their Watsons Bay homes. "I rem-ember racing home, afraid I'd be in trouble," Mr Horler said. "I felt I'd get a belting from my dad for being late, having lost my hat and schoolbag and drenched my school uniform." No trouble followed from Mr Horler - the town clerk of Vaucluse Council - and young Ken went back to school the next day by ferry. "There was no such thing as counselling," he said. "I just got on with it."

Mr Horler's memories of the disaster have been included in a book by Steve Brew called Greycliffe: Stolen Lives that will be launched this weekend.

Mr Brew said he started researching the Greycliffe story to find out more about his great-granduncle, Captain Thomas Carson, who was the pilot on board the Tahiti. "There had been articles written about it, but there was no complete book about the Greycliffe," Mr Brew said. "I thought it was important to tell the story and started a project that took nearly four years."

Research took him through the coronial records in the State Archives and the four court cases that followed the tragedy, as well as interviews with friends and relatives of survivors and victims. Mr Brew said the court action failed to quash the rumours, doubt and controversy that surrounded the accident. The dead ranged in age from two years to 81 - among them Australia's first female pilot, a six-term mayor of Leichhardt, three doctors and the science master of Sydney Boys High.

"I believe the Greycliffe was way off her usual course when the Tahiti hit," Mr Horler said. "We'd seen it approaching, it was very big but we did not know what would happen. "The tragedy hit this area very hard, as it was a small, close-knit community and everyone knew someone who had died."

Mr Horler went on to spend six years in the RAAF fighting the war in the Pacific, and was a chartered accountant after the war. Horler Avenue at Parsley Bay was named after his father, and he is the proud grandfather of award-winning actress Sacha Horler.

Greycliffe: Stolen Lives by Steve Brew, Navarine Publishing, $34.95, is available at the Australian National Maritime Museum, Museum of Sydney, and NSW State Library bookshop.