The race is on to save a pod of pilot whales beached on a remote sandbar off Australia's island of Tasmania.
Scientists estimate between 90 to over 200 of the animals are stranded in the shallow water.
Rescue operations began on Tuesday (September 22) morning.
Wildlife biologist Dr Kris Carlyon says the operation could take days: "We've got animals spread over a large area in a really challenging location, so we're gonna basically take the animals with the best chance to start with. And the ones that we're able to deal with so, some animals may be simply too big or in an unsuitable location."
The rescue will be labour intensive physically pushing the animals or using specialized cloth and pontoons to drag them to deeper water.
Pilot whales are a species of oceanic dolphin that grow to 7 meters long and weigh up to 3 tonnes.
Around 40 government scientists, 20 police officers, fish farmers and volunteers are involved in the rescue effort, the hardest experts say they have encountered yet.
Scientists do not know why whales beach themselves.
But they say when the animals travel in pods, they're known to follow a leader, and gather around a whale that is injured or in distress.