ELEANOR HALL: To Western Australia now, and the search has been called off and questions are now being asked about how and why a 26-year-old Western Australian man has become the nation's latest shark attack victim.

Authorities are confident that it was a large Great White shark which took the young skipper on Saturday, while he was snorkelling with friends.

The attack comes just months after another man was killed by white pointers off a popular beach in South Australia, heightening the already common fear surrounding shark attacks, as Tanya Nolan reports.

TANYA NOLAN: It was a good day on the Abrolhos Islands. The sun was shining, the water was clear: perfect conditions for the skipper of the charter boat The Matrix, Geoffrey Brazier, and his passengers to go snorkelling.

The spot they chose at the southern end of the archipelago, which hugs the West Australian coast, about 60 kilometres off the coast of Geraldton, and more than 500 kilometres north of Perth, is on the edge of the continental shelf ? a popular haunt for large sharks.

And according to eyewitnesses like Rod Plug, Mr Brazier didn't have a hope against the 6-metre giant which made a beeline for him.

ROD PLUG: Yes, I did see the shark. It was very large, very wide. We estimated over six metres long. Very dark on top, white underneath, a pointed nose, and a dorsal fin that was almost a metre high. We? well, I would identify it as a Great White shark, yes.

TANYA NOLAN: The West Australian Fisheries Department and police have called off their search for the Great White that took Mr Brazier's life.

Rory McCauley, shark researcher with Fisheries, says the shark is most likely long gone from the area. He also says the shark they're looking for may be smaller than suggested.

RORY MCCAULEY: We'd urge a bit of caution in judging the size of a shark from a boat, which even under ideal circumstance is quite tricky. So, I guess the total size should be treated with some caution, but it was undoubtedly a very big shark.

TANYA NOLAN: So, you suspect it could've been less than six metres?

RORY MCCAULEY: Um, well, six-metre White Pointers are extremely rare. They do reach a maximum size of about seven metres, in fact upwards of seven metres. But the bigger sharks of six-metre plus are really quite uncommon, but I certainly wouldn't discount it, but sharks smaller than that size are somewhat more common.

TANYA NOLAN: Mr Brazier is the third fatal shark attack victim in WA in the last four years, and his death has left people as bewildered as ever about what prompts such a tragic event.

But Mr McCauley warns there are no straightforward explanations.

RORY MCCAULEY: There are a number of different theories as to why these events happen, but I think, you know, the circumstances surrounding each attack are unique to each circumstance, and you know, it's very difficult to put yourself in the mind of an ancient fish like a Great White shark.

So, I don't think there is any one particular reason why this happens, and there's, you know, it's very speculative to start wondering why this particular event took place.

TANYA NOLAN: One of the questions that is being asked is whether it was a wise choice to snorkel on the edge of the deep continental shelf where large sharks are known to inhabit.

Fisheries Regional Manager Russell Dyson says there's only one way to avoid a fatal shark attack.

RUSSELL DYSON: Well, I think it is a freak accident. Anything like this can be avoided by simply not going in the water, but it is the shark's domain, and if we choose to go in there we have to play on their terms.

TANYA NOLAN: Is this area a well-known haunt of Great White sharks?

RUSSELL DYSON: Oh, not at all a well-known haunt. We know White sharks travel up and down the edge of the continental shelf off Western Australia, but it's not something that you would expect to see there.

TANYA NOLAN: Do you think that charter boat operators, given the duty of care that they have to the guests onboard, should perhaps do a bit more research or ask authorities about the best places, or the more safe places to take their guests snorkelling or diving?

RUSSELL DYSON: Well, I don't think that's really an issue in this, on the basis that there is no indication that there was any likelihood of a Great White shark being there.

TANYA NOLAN: So, you just don't think that this place was any more risky than any other part of the Abrolhos?

RUSSEL DYSON: Well, certainly in the deeper water you're likely to meet a different species of fish and that out there, but, look, there's lots of sharks in the ocean, and it's just terribly, terribly bad luck that it happened there.

ELEANOR HALL: Russell Dyson is the Geraldton Regional Manager of Fisheries Western Australia, and he was speaking to Tanya Nolan.