If faced with a five metre white pointer in the waters off Western Australia, not many people would swim toward it to get a closer look but that's exactly what Paul Hosie did over the weekend.

Mr Hosie says he has seen plenty of large marine life underwater including whale sharks, manta rays and seals but this was his first encounter with the ocean's top predator.

Paul Hosie was diving at the HMAS Swan wreck site just off the coast of Dunsborough on Sunday when he noticed a big black shape go past him just 10 metres away.

"When I looked at it there was no doubt what it was; it was dark above with white below, just the enormous bulk of it and a massive tail fin."

The unmistakable sight of a great white shark would leave most people swimming in the opposite direction but Mr Hosie was fascinated by the sight and wanted to get closer.

"After about five minutes of observing it, I decided that I wanted a closer look. A lot of people would say that was a foolhardy stupid thing to do but I had a shark shield and I know the behaviour of these things.

"People are taken from the surface, that's how these things feed and attack not at depth, not normally."

Mr Hosie is an ex-Navy member who has been recreational diving for 18 years and was diving with his fiancee Christie at the time. He says he has seen many sharks over the years but this was by far the largest shark he has seen while diving.

Mr Hosie and his partner were wearing an 'electronic shark deterrent' at the time, which is a device that straps around the ankles with an antenna hanging below the diver which emits an electric field that induces spasms in a shark's snout.

However, the effectiveness of the device was about to be tested by Mr Hosie as he swam down away from the wreck and down to the ocean floor, the same level as the shark.

"It actually did take an interest in me because something had moved into its space and it swam straight towards me from about 20-30 metres away.

"At about 10 metres away when it was still heading straight towards me and I established eye contact, that's when I thought, 'maybe this wasn't such good idea'.

"But I had faith in my shark shield otherwise I wouldn't have been wearing it and about 5 to 7 metres away, it turned away from me."

Mr Housie has been wearing the electronic shark deterrent since a fellow diver was killed by a great white in 2008 at Port Kennedy, a location that Mr Hosie frequently dived.

"I don't go diving to put my life at risk; I dive to enjoy the experience so from then on I've worn a shark shield all the time."

You can listen to Paul Hosie's full interview with ABC's Geoff Hutchison above where he describes his close encounter with a great white shark.