More than 40 sperm whales have died after a pod of about 50 became stranded off southern Australia, wildlife officials have said.
Rescuers have been trying to pour water over the survivors to keep them alive.
The pod is trapped on a sandbar 150m (500 feet) offshore from Perkins Island on the northwest coast of the island state of Tasmania.
Rescue is proving difficult because of the whales' immense size, and because the area is only accessible by sea.
A spokeswoman for Tasmanian Parks and Wildlife Services, Liz Wren, told reporters that rescuers thought seven or eight whales may still be alive, although other reports suggest just two may have survived.
"The males are as big as 18m, females 12m, weighing in between 20 and 50 tonnes," she said.
She said while rescuers had been able to save some long-finned pilot whales after another mass stranding on a Tasmanian beach in November "sperm whales are an entirely different kettle of fish and much more difficult".
"And it's much harder on them when they strand because the great weight of their bodies puts more pressure on their internal organs," she said.
Moving the carcasses of the dead whales could also pose problems because they are stuck on the edge of a major navigation channel for a fishing port.
A team of six wildlife rangers reached the survivors by dinghy early Friday and were attempting to keep their skin wet, until the next high tide.
In November more than 150 long-finned pilot whales died, with many sustaining deep cuts after thrashing against rocks, after beaching themselves on the remote west coast of Tasmania state.
Australia's southern island of Tasmania experiences about 80% of whale beachings in the country.
The reasons for the latest beaching were unclear, but Ms Wren said rough sea conditions and the narrow channel that the pod had been navigating between the island and the mainland could be part of the explanation.
Mass strandings of whales occur periodically in Australia and New Zealand, as the whales migrate to and from Antarctic waters, for reasons that are not entirely understood.
Theories include disturbance of echo-location, possibly by interference from sound produced by human activities at sea.
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