The fall occurred Tuesday night between 4.00pm and 9.00am.

Brad Camrie from Twelve Apostles Helicopters said: "We first noticed that the water looked a little different." He added, "Looking at it, you wouldn’t know there had been an archway."

"The southern coastline is always changing. Nature is constantly shaping and reshaping it,” said Natasha Johnson, Acting Ranger in Charge - Port Campbell.

"The changing coastline is why we have to be careful about visitor safety. Parks Victoria and the Department of Sustainability and Environment conduct maintenance works in areas prone to erosion and landslips, including geotechnical assessments around infrastructure to reduce the risk to visitors and the environment."

The last significant collapse on the southern coastline was on Sunday 2 July 2005 when a large stack fell at the Twelve Apostles.

"There was significant visitor interest when one of the Twelve Apostles fell down, we expect this event may do the same," said Ms Johnson.