A police spokeswoman said the victim and his brother were diving off Stratham Beach, a 3-hour drive south of Perth, The Australian reported. The brother was not hurt.
The victim's body was taken to the Port Geographe Marina near Busselton.
The man was the first person to be killed by a shark in 2012 in Western Australia, PerthNow reported. There were fatal attacks in September and October last year, and a man who vanished during his daily swim in October is believed to have been killed by a great white shark.