One of south-west Victoria's coastal landmarks, the Loch Ard Gorge, has changed shape, with part of the cliff falling away.

Loch Ard Gorge is one of the main tourist attractions of the Shipwreck Coast.

But now a freestanding part of the cliff - which is shaped like a bridge - has collapsed.

It has left two rock formations like those of the nearby 12 Apostles.

The Loch Ard Gorge in south western Victoria before and after it changed shape overnight. (Parks Victoria)

Peter Abbott from the Flagstaff Hill Maritime Village says it is hard to tell the arch was even there.

"You can tell how fragile the coast is, once it actually hits the water it basically dissolves, like sugar I guess," he said.

Several of the Great Ocean Road coastline's famous rock formations have been eroded by the sea recently.