Mr Brierley had visited the wreck of the SS Yongala, about 12 miles off Queensland near Townsville. As soon as he entered the water he became swept away by the current. He became seriously worried when he realised that he had not replaced his personal locator beacon after taking it from his scuba tank to clean it.
According to The Times, Mr Brierley, originally from Bury but now living on the Sunshine Coast, said from his hospital bed: "I'd taken it out after the last deep dive to make sure the case was dry. That was a tragedy because if that had gone off, the helicopter would have gone straight to me."
He said that instead he suffered a "nightmare scenario" after he could see a rescue helicopter overhead, but they did not see him.
Friends raised the alarm after he failed to return, and rescuers found the boat on Sunday night but didn't find the diver until Monday morning.
According to Sky News, Mr Brierley said: "I was feeling exhausted and when I thought the choppers had missed me, I didn't think I was going to make it to the shore."
He said he was being swept south and planned to swim for Cape Upstart, adding: "I didn't relish that because I know there are a lot of sharks in Cape Upstart Bay because I've seen them.
"My biggest fear really was the sharks ... and especially first thing in the morning after I'd swum all night, you know, the birds feed when the sharks and the mackerel are all around and there was a couple of flocks of birds really close to me, I thought 'oh, this isn't good'.
"I was debating in my mind which would be the preferable way to go...drown or getting eaten by a shark."
"A couple of the birds were flying overhead sizing me up as a possible meal and I just yelled to one of them 'go and get some help'."
Rescuers saw Les as they were about to leave the area to refuel.
Alan Griffiths was lowered down from the helicopter to rescue him, and said he was "very, very lucky". He was spotted around 31 miles from the dive site.
Mr Griffith told Sky News: "I said to him 'G'day mate, do you want a lift?' and he was a bit shaky and jittery."
According to the Daily Mail, he added: "He put his hand out so I could shake it – [that] says a little bit about him, and the type of gentleman he is.
"He'd gone by himself, which is a bit naughty, he jumped in the water from his boat and then realised the current was so strong and he simply couldn't get back."
Les was take to hospital with mild hypothermia and says that finally being rescued was a "magic feeling".
10 Easiest Places To Get Eaten By A Shark
10 Easiest Places To Get Eaten By A Shark
New Smyrna Beach in Florida has the dubious honour of having more shark attacks annually than any other beach. The beach is part of Volusia County, which accounts for roughly 37% of Florida’s 663 attacks since 1882.
It is estimated that anyone who has swam there has been within 10ft of a shark, according to National Geographic. However, there have never been any fatalities on New Smyrna.
However, that can't be said for the rest of Florida. Since 1988, there have been 6 fatalities.
The number of fatal, unprovoked shark attacks in South African waters between 1990-2009, is 22, according to the KwaZulu Natal Sharks Board. There have been 136 attacks in total.
In 2012, there were four shark attacks in South Africa, three of them fatal, according to the International Shark Attack File.
Picture: A woman enters the water as workers aboard a boat, right, place a shark exclusion net at Fish Hoek beach, on the outskirts of Cape Town, South Africa, Friday, April 5, 2013.
There have been 207 unprovoked shark attacks in Australia over the last 20 years, and 124 of those occurred in the last 10 years, reports Australian Geographic.
According to The West Australian newspaper, Western Australia has become the deadliest place in the world for shark attacks, after the fourth death in seven months occurred in 2012.
Picture: Shark warning sign on Botany Bay beach. Sydney, Australia.
In the past 20 years Brazil has become an increasingly hazardous place to go swimming.
While the north-east coast might have a stunning coastline and bath-temperature waters, the BBC report that off the shore of Recife are many aggressive sharks, which has made this one of the most dangerous places in the world to swim.
Brazil's sharks appear to be some of the most dangerous in the world. The death rate of 37% (21 of the 56 attacks in 20 years) is much higher than the worldwide shark attack fatality rate, which is currently about 16%, according to the Florida State Museum of Natural History.
Picture: Placard warns about a shark hazard in Boa Viagem beach in Recife, northeastern Brazil on September 11, 2012.
After 14 unprovoked shark attacks were reported in Hawaii in 2013, according to hawaiisharks.com, locals have become increasingly nervous about the risk posed by sharks
From 1828 to December 2013 there have been 128 total unprovoked shark attacks in Hawaii, 10 of which were fatal attacks, according to the International Shark Attack File at the Florida Museum of Natural History.
Picture: Japanese tourists stroll along Waikiki Beach in Hawaii, following a shark siting in 2001, which closed the beach.
California has had 109 confirmed unprovoked shark attacks since 1926, according to the International Shark Attack File, and the state ranks second in the U.S. for shark attack frequency.
There have been 10 fatal attacks, and the last was just two years ago in Santa Barbara in 2012.
Papua New Guinea has had nearly 50 shark attacks (half of them fatal) .
The Guardian report that the country has a disproportionately high number of shark attacks, considering its small population size, because of the country's location, with extensive seas coasts and warm climates.
Picture: Trobriand Island In Trobriand, Papua New Guinea
Since 1837, 71 shark attacks and two fatalities have occurred in South Carolina, according to the International Shark Attack File at the Florida Museum of Natural History.
Of those, 16 attacks are recorded off the beaches of Horry County, where the town of Myrtle Beach is famous as a tourist destination, according to Yahoo.
Luckily, there have been no fatal shark attacks in South Carolina since 1852. But in 2012, South Carolina had a worryingly high level of incidents, when five attacks were reported.
Picture: Myrtle Beach
Despite its size, New Zealand has a relatively high incidence of shark attacks, according to The Encyclopedia of New Zealand.
Since 1852 there have been 44 recorded unprovoked attacks (compared with 39 in the whole of Europe since 1847).
A third of New Zealand attacks occurred between Ōamaru and the Otago Peninsula, probably because sharks are attracted by the high numbers of seals, dolphins and pilot whales in that area.
Picture: A flower tribute at Muriwai Beach near Auckland, New Zealand, after a shark killed Adam Strange in 2013.
Mexico has had 42 shark attacks (22 fatalities) since 1880.
Picture: People walk along Troncones beach in Mexico's Pacific Coast village of Troncones in 2008, after sharks attacked three surfers in the area in less than a month, two fatally.