CANBERRA, Australia  —  A 20-foot shark tore a man in half as he was snorkeling off Australia's west coast, police said Sunday.

The man, a pleasure boat deck hand who was snorkeling with tourists, died instantly in the attack Saturday afternoon off the Abrolhos Islands about 250 miles north of the Western Australia state capital, Perth, said Police Inspector George Putland (search).

"The 26-year-old man was bitten in half by the 20-foot animal and death seemed to be instantaneous," said Putland, adding that the man's body was not recovered. The search for the remains resumed Sunday.

The species of shark was not yet known and it was not clear how many people were in the water with the victim at the time of the attack. No one else was injured.

Area residents have speculated that a great white shark or tiger shark was responsible. There were no immediate plans to hunt the shark.

The fatality is the first in Australian waters since December, when an 18-year-old surfer was bitten in half by a 16-foot great white shark off a beach in the southern city of Adelaide. A week earlier, a shark killed a 38-year-old diver spear fishing on the Great Barrier Reef (search) off northeast Australia.

The latest attack was the first to occur off the west coast since two sharks killed a 29-year-old surfer south of Perth in July. Experts said then that sharks were not previously known to hunt in pairs.