Officials from Tasmania state's Parks and Wildlife Service rushed Sunday in four-wheel-drive vehicles to the remote site at Sandy Cape after the long-finned pilot whales were spotted by air a day earlier.
A helicopter crew that arrived late Saturday found about a dozen of the whales injured but alive, but by the time the road crew arrived all of the group were dead, said Warwick Brennan, a spokesman for the service.
The coastline is strewn with reefs and jagged rocks, making it much more dangerous for the stranded whales than if they had landed at a sandy beach, said Rosemary Gales, another wildlife service official.
"Because of the physical beating they take from stranding on rocks and surf, compared to sandy beach strandings, animals die more quickly," said Gales.
About 15 whales that seemed to be part of the same pod began swimming away from the area after the last of the stranded whales died. The second group swam near those stranded and may have been responding to cries of distress, Brennan said.
The operation comes one week after rescuers saved 11 pilot whales among more than 60 stranded on a beach in northwestern Tasmania, which is an island.
Strandings are not uncommon in Tasmania, where the whales pass by on their migration to and from Antarctic waters. It is not known why whales get stranded.