Melbourne, Mar 10 (IANS): Australian scientists have discovered five new, submerged "Apostles" -- limestone columns -- near one of Australia's most iconic tourist landmarks, the Twelve Apostles.

Five limestone sea stacks, coined the "drowned Apostles", were found 50 metres underwater and six km away from the original Apostles site, on Victoria state's south coast, Xinhua news agency reported.

The submerged stacks, which stand four to six metres in height, are believed to be 60,000 years old, according to University of Melbourne researchers.

The Twelve Apostles, along Victoria's Great Ocean Road, is among Australia's greatest natural marvels.

The cluster of stand-alone boulders, which stand approximately 30 to 40 metres tall, were nicknamed the Twelve Apostles in the 1920s, despite the fact that only nine were visible.

After losing one of the nine Apostles in a dramatic collapse in 2005, the landmark has managed to boost its portfolio by five following the latest underwater find.

Associate professor David Kennedy from the University of Melbourne's School of Geography said it was the first time linear stacks of limestone had been detected on the seafloor.

Melbourne University PhD student Rhiannon Bezore, who made the discovery by using sonar data of the surrounding seafloor, said a number of critical environmental factors had to be present to shape the sea Apostles.

"The main factor is that through the past geological changes, sea levels have risen at such a fast pace," Bezore said.

In Bezore's study, published in the Journal of Coastal Research on Thursday, she also established that the original cliffs were eroding at a rapid pace of around 30 cm annually.