Seventy pilot whales have been saved on Tasmania's west coast after Australia's worst mass stranding on record.
About 380 of some 470 whales are confirmed to have died after the pod got into trouble at Macquarie Harbour on Monday.
"We're retrieved 70 whales or thereabouts off the sandbar and released them out to sea," state Parks and Wildlife manager Nic Deka said on Thursday morning.
There are roughly 20 stranded whales still in a good enough condition to be saved, with their survival window likely to close within the next day.
Another four will have to be euthanised for welfare reasons.
"These are animals that we've given a chance. We've tried to release them, they haven't done well," wildlife biologist Kris Carlyon said.
Crews are now faced with the grim task of collecting decomposing carcasses, which are likely to be disposed of at sea if conditions allow.
There is a risk they could attract sharks and disrupt oxygen levels in the harbour, which may harm marine live.
"As the whales start to decompose, they will bloat and float and with wind and tide, they'll drift," Mr Deka said.
"They could cause a significant navigation hazard if we don't contain them."
Mr Deka said volunteer crews were beginning to tire on the fourth day of the mission, which has been conducted in cold waters and often rainy weather.
It is the biggest mass stranding in Tasmania and likely the largest on record in Australia.
It surpasses a 1996 beaching of 320 pilot whales at Dunsborough in Western Australia.
Previously, Tasmania's largest mass stranding involved 294 long-finned pilot whales at Stanley in 1935.
One large group was initially discovered stranded near the harbour's head on Monday, with rescuers on Wednesday spotting 200 dead whales a few kilometres away.
It is thought the two groups were part of the same pod that ventured close to shore to hunt.
"Pilot whales are incredibly social and maintain strong social bonds with each other and have been known to be found in groups up to 1000," marine scientist Dr Vanessa Pirotta told AAP.
"The ability for them to stick together and follow the leader is something we see often with these animals, which is why it is so heartbreaking."
