The four-metre (13-foot) white pointer was filmed thrashing around just off Coronation Beach, 430 kilometres (270 miles) north of Perth, and was later found on the sand.
The Western Australia Department of Fisheries said it had no visible signs of injury or disease, but had a large sea lion lodged in its throat.
"This could explain why the shark was exhibiting such unusual behaviour in shallow waters off Coronation Beach," said research scientist Rory McAuley in a statement.
"It is possible that the shark was trying to dislodge the blockage.
"Such a large object may have damaged the shark's internal organs or impeded water flow into his gills, contributing to his death," he added.
"Alternatively, the shark may have accidentally become stranded in his attempts to get rid of the obstruction."
Brad Tapper filmed the shark as it struggled in shallow waters and posted the clip on YouTube.
Tapper, who had been at the beach with his children, said a dog walker first noticed the shark when his pet refused to go in the water.
"When we spotted it, it was about 50 metres off the shore. We thought it was a diver or something," he told the West Australian newspaper.
"It was kind of surreal, you're watching it and you don't realise how rare it is at the time until you get home and have a look at the footage."
After it beached itself, some onlookers attempted to drag the shark out to sea using a tow rope, but the animal returned to shore soon after.
"We went to look at it and got within three or four metres of it but it started kicking and thrashing around again so we thought it was time to leave," Tapper said.
Share
