Rescuers area attempting to refloat some of the whales that are stuck on sandbars at Macquarie Harbour, near Strahan.

Marine Conservation Program wildlife biologist Kris Carlyon said progress will be slow, with conditions and the half-submerged whales making rescue efforts tricky.

“This morning’s phase will be critical in determining what is possible,” he told reporters.

“Basically we’ll take the animals with the best chance to start with and the ones that we are able to deal with.

“Some animals may be simply too big or in an unsuitable location.”

Mr Carlyon said about one-third of the whales had already died as of Monday evening and most were inaccessible by boat.

“In terms of mass strandings in Tasmania, this is the trickiest we’ve had to deal with,” he said, adding the mission could take days.

About 60 people are helping with the rescue, including 40 parks and wildlife staff and personnel from nearby fish farms, which have supplied boats.

Members of the public are being urged to stay away from the high-risk rescue operation.

“These are large animals and if they’re thrashing around, they’re dangerous,” Tasmania Parks and Wildlife regional manager Nic Deka said.

The whales are spread across two sandbars, while 30 stuck on a beach have died.

Carlyon said pilot whales were a robust species and the survivors had a chance of lasting several days on the sandbars if the weather stayed cool.

“It’s ugly for people on the ground but as far as the whales go, it’s ideal,” he said.

The whales got into trouble on Monday morning but the rescue couldn’t begin until marine specialists were able to survey the scene.

Carlyon said multiple rescue methods would be trialled and a lot would depend on how the whales responded.

It is understood to be the biggest mass stranding in Tasmania in more than a decade.

The social pilot whales, which travel in groups of up to 1000, could have been drawn close to the coast to feed or because the pod followed the misadventure of a few individuals, Carlyon said.

-AAP