Sydney - A sea-and-air search failed to find any trace of a man who was attacked by a shark while snorkelling for crabs just six metres from the beach in Western Australia on Saturday, news reports said.

One witness reported seeing blood in the water, and police closed the beach at Port Kennedy, south of Perth, warning swimmers in the area to exercise caution, ABC radio reported.

The victim was local banker Brian Guest, 51. Family spokesman Steve Kent said that he would not want the shark to be hunted and destroyed.

He said Guest had spent many years diving and fishing and knew the dangers of being in the water.

"It's nature and we should pay respects to nature and nature's ways," Kent said.

Guest was snorkelling with his 24-year-old son, who called for help when his father was attacked. (dpa)