A great white shark killed an American recreational diver on Saturday in a third fatality in recent weeks off southwest Australia that has shaken beach-loving residents and sparked fears of a rogue predator targeting humans.
Australia averages fewer than two fatal shark attacks a year nationwide.
The state government has promised to hunt the killer and is considering more aircraft surveillance off west coast beaches as whales migrating in larger numbers attract more sharks.
The first sign that the 32-year-old American man, whose name and hometown have not been released, was in trouble as he dived alone was when a stream of bubbles erupted on the ocean surface beside his 25-foot dive boat, police said.
His two horrified companions on the boat saw his lifeless body surface and a 10-foot great white swim away, Western Australia Police Sgt. Gerry Cassidy said.
The shark struck 500 yards north of the picturesque tourist haven of Rottnest Island, which is 11 miles west of a popular Perth city beach where a 64-year-old Australian swimmer is believed to have been taken by a great white on Oct. 10.
Authorities cannot say whether the American was killed by the same shark that is believed to have taken Bryn Martin as he made his regular morning swim from Perth's Cottesloe Beach toward a buoy about 380 yards offshore.
But an analysis of Martin's torn swimming trunks recovered from the seabed near the buoy pointed to a great white shark being the culprit. No other trace of Martin has been found.
"It's a cloudy old day today which is the same as we had the other day with Cottesloe, and they're the conditions that sharks love," Cassidy said.
The American had a work visa and had been living in a Perth beachside suburb north of Cottesloe for several months.
The tragedies follow the death on Sept. 4 of 21-year-old bodyboarder Kyle Burden, whose legs were bitten off by a shark described as 15 feet long at a beach south of Perth. Witnesses were unsure of the type of shark.
While great whites trail the migration of whales between Antarctic and northwest Australian waters, the west coast has not been widely regarded as a shark danger zone for humans.
Premier Colin Barnett, the leader of the state government, took charge of the official response on Saturday, telling reporters that the shark will be hunted and killed if possible.
He said fisheries officers will spread bait in the area of the attack to try to catch the shark.
While great whites are protected under Australian law, Barnett said his government would consider increasing the numbers of other sharks that commercial fishermen can catch, following reports that shark numbers have increased.
He said his government was also looking at increasing aerial shark patrols over popular beaches.