Authorities are "quietly confident" the four whales put back out to sea from Bunbury Harbour will survive after a spotter plane failed to locate them on Tuesday morning.
A pod of about 20 long-finned pilot whales were discovered smashed against rocks in Bunbury Harbour on Monday morning.
The Department of Parks and Wildlife later confirmed 12 of them had died, while more than 50 volunteers and wildlife officers spent hours herding four of the whales back out to sea.
DPaW senior wildlife officer Doug Coughran said the spotter plane did a 40-kilometre sweep of the Bunbury coast on Tuesday morning, but failed to see any whales.
"We are cautious but confident about the whales," he told Fairfax Media. "But we know they do come back to shore.
"But we also know if we get to them quick enough, there is a 70 per cent chance they will survive."
Mr Coughran said an autopsy was done on nine of the 12 whales overnight and none appeared to be sick.
He said as long-finned pilot whales were social animals, when one headed for the shore, the rest of the pod followed.
"It's one-in, all-in, with the whales," he said.
"They are a deep-ocean species, so it's like us been trapped in a dark room, we walk into a wall when fumbling to find the door.
"When they are in the shallow waters, their sonar gets all screwed up."
Meanwhile on Tuesday morning Surf Life Saving WA advised three, two metre tiger sharks were sighted 20 metres offshore at Bunbury's McKenna Point where the whales had beached themselves the day before.
Nigel Schofield from the Department of Fisheries’ Shark Response Unit said people should take extra caution.
“We urge people to stay out of the area, report any shark sightings to Water Police on 9442 8600 and keep an eye on SharkSmart or the SLSWA Twitter for the latest sightings," he said.
“The Department of Fisheries is providing assistance as required to the Department of Parks and Wildlife, which is managing the whale stranding incident.”
