During May and June 1974, three East Coast Low storms caused major damage along the Sydney coastline. The largest of these is now known as the 'Sygna Storm', named after the 53,000-tonne Norwegian bulk carrier Sygna — the largest shipwreck in Australian history — that at 2am on Sunday May 26 was driven ashore by large storm waves at Stockton Bight in Newcastle.
On Thursday May 23, a low-pressure system developed about 500km southeast of Sydney that led to increasing wave heights from the southeast as the system deepened. Then, about midnight on Saturday May 25, an intense low-pressure cell developed offshore south of Sydney and moved up the coast. The peak of the storm passed through Sydney about 1am on Sunday May 26, and reached Taree five hours later, after which it weakened and moved back out to sea. At the height of the storm, winds gusted at up to 165km/h and the significant wave height (the average height of the highest one-third of the waves) off Sydney reached about 9m.
At Bilgola the beach was extensively eroded and beachfront property damaged. The location of this geocache marks the spot where a private swimming pool was destroyed. It is fun to stand at the geozone and - using the photo below - look at what has and hasn't changed at Bilgola after more than 40 years.
And don't forget to bring your swimmers and a towel - if an ocean swim between the flags is not what you are looking for, the 50m Bilgola Rock Pool is close by at the southern end of the beach.
Source: John Morcombe (Manly Daily, June 22 2016) https://tinyurl.com/ya3e3ylb