Authorities are hunting for the shark which killed a diver near Rottnest Island off the coast of Western Australia.
The man, a 32-year-old American, has been diving and spear fishing alone near the popular tourist resort about 20 kilometres west of Perth.
Witnesses say the shark was a three-metre white pointer.
Police say it was the third fatal shark attack off Australia's west coast in two months.
Western Australia Premier Colin Barnett has ordered that the shark be caught and killed, the ABC reports.
Department of Fisheries spokesperson Tony Cappelluti says six lines, each carrying a fully baited shark hook, will be set on Sunday.