It was 3pm on a hot Sunday in February 6, 1938 when three massive waves smashed Bondi Beach in quick succession.
Five people drowned on the day known as Black Sunday, one of the deadliest days on any Australian beach.
Are all rips the same?
No matter how experienced you are, a rip can put even the strongest swimmers in danger in a matter of minutes. Here's how to pick them.
Nearly 200 surfers were swept out to sea and 35 were unconscious when rescued on that day by the "gallantry" of the public and lifesavers, reported The Sydney Morning Herald.
Eyewitnesses reported waves that resembled tidal waves.
Experts now believe that the "sudden backwash of huge seas" at Bondi that day was caused by a flash rip.
Flash rips are among the most dangerous and unpredictable kinds of rips, coastal geomorphologist Dr Rob Brander told Rip Current Heroes, a new documentary on rips screening on National Geographic which will also be provided free to schools to educate children on the dangers of rip currents.
They can suddenly occur "anywhere there's suddenly been a large group of waves breaking, and it pushes the rip out and then it just disappears and then it might come up a little bit further down the beach, it might come back ten minutes later", he said.
On Black Sunday, more than 70 rescuers used belts, rubber floats and anything else they could grab in a frantic attempt to save people. Many of the helpless swimmers, particularly the men, panicked.
"Some of them (rescuers) had to fight for their lives with men who seized them and, in their frenzied struggles, dragged them down. The women surfers showed coolness and courage," said the report.
A similar flash rip was also responsible for the death of Ryan Martin who went to the rescue of a seven-year-old girl Rihanna Milabo, who was caught in a rip at Dreamtime Beach on March 25, 2016.
In a desperate attempt to save the young girl, a succession of people went to her rescue, each to be exhausted by the struggle.
In the wake of the rip, police found unclaimed clothing in the dressing sheds. Some was identified as belonging to a victim, Michael Taylor of Goodchap Street, Surry Hills.
The other unidentified clothes, a white cotton singlet, a grey striped shirt by the brand Richards, and a pair of tan shoes from David Jones, were thought to belong to the other victims, the Herald reported.
Today rips remain a constant on Bondi Beach, the source of many rescues chronicled in the television reality show Bondi Rescue. Academic research has shown the television show has improved public awareness of rips and beach safety among viewers.