Rich-lister 'Aussie' John Symond is the biggest donor to the GoFundMe appeal for the victim of the Coogee Beach shark attack, but modestly brushed off his kindness.

The home loan tycoon confirmed to the Daily Mail that he had tipped in $5,000 for new mum Leah Stewart, 35, after she was mauled by a great white shark on Saturday.

The school teacher was swimming between the flags and close to the shore when she was attacked, while her one-year-old daughter was on the sand with a friend.

Ms Stewart was plucked to safety by off-duty lifeguard Charlie Verco who brought her back to shore with his paddleboard as she was losing consciousness.

Surgeons later had to amputate her left arm and she lost so much blood in the attack, paramedics had to give her multiple transfusions on the beach.

Ms Stewart's plight saw Aussies contribute more than $300,000 to the GoFundMe within 24 hours of it being launched.

Among them was Mr Symond, the founder of Aussie Home Loans, who has a net worth of $727million according to the latest Australian Financial Review Rich List.

But he told the Daily Mail on Tuesday: 'It is no big deal on my part.

'If you can do something for people who are in strife, you do it. She is a young mum with a tough future ahead so it is good to be able to help in some way.

'It is the culture of Australians to help people when you can. Whether you can only offer up a dollar, or my few thousand.'

Mr Symond founded Aussie Home Loans in 1992 after borrowing $10,000 from his brother, and went on to become one of Australia's richest people. 

Mr Symond, who owns a spectacular $200million harbourside mansion at Point Piper in Sydney's eastern suburbs, said he was moved to help due to his love of the ocean.

'I spent a fair bit of time boating and I live on the waterfront,' he said. 'To see [this happen] to someone who loves swimming...she did everything right.

'That young lady did everything right, and [now] has a baby and terrible obstacles in front of her.'

She was airlifted to St Vincent's Hospital in a critical condition and has undergone several operations on her life-threatening injuries, including the amputation of her arm.

Her family expects more surgeries in the coming days. 

Daily Mail understands another $2,000 was contributed by Harley Oliver, the husband of Gold FM radio personality Amanda Keller.

Mr Oliver, who suffers from Parkinson's disease, did not return phone calls on Tuesday, and has long lived in Coogee with his wife.

The Daily Mail has approached Keller for comment.

Another well-heeled Coogee resident, wealth manager and author Nicolette Rubinsztein, donated a further $1,000.

Ms Stewart's brother Joshua Stewart created the GoFundMe campaign just before 3pm on Monday to help with her recovery, revealing that her arm had been amputated.

He aimed to raise $450,000. 

Within 18 hours, the fundraiser had raised more than $300,000, with donations ranging from about $20 to $5,000. 

A friend of Ms Stewart urged people on Facebook to donate blood if they were unable to make a financial contribution. 

'Leah is a part of my mother's group and is one of the kindest people. We would all sit on the Coogee hill and take turns having swims while the bubs played,' she wrote.

'She was the first one to reach out to anyone she thought was struggling while going through our first year of motherhood together.

'Giving blood is also a great way to honour Leah.

'She received multiple units on-site of the accident when the chopper arrived, and this contributed to saving her life on the day.'

In the fundraiser, her brother wrote: 'Leah remains in a critical condition on life support and has undergone multiple surgeries in the days after the attack.

'Tragically, her treatment has required the amputation of her arm, and more surgeries are scheduled for the coming days.'

He said her recovery would be a long process and all donations would go towards rehabilitation, prosthetics and improving her quality of life.

Mr Stewart confirmed his sister was swimming between the flags and close to the shore when the shark attacked, and thanked first responders who helped save her.

Mr Verco, 25, was paddleboarding about 100m from Ms Stewart when the attack occurred.

He immediately paddled towards Ms Stewart and helped lift her from the water.

'The water got very bloody and she got taken under and after a few seconds, popped up again and the shark had let her go,' he told ABC News.

'All I really wanted to do was to go to shore, obviously, but because I was the only one on any craft near her, I was, like, if I don't, I'm not here to help her, no-one is.

'She was lucid enough to say, "Help", and respond to instruction, but she was very much in shock and definitely freaked out and wasn't able to have conversation.

'That was when I was able to actually get close enough to her and get her to grab the front of my board.'

Mr Verco said he tried to comfort her, telling her 'We're almost ashore' and 'You're doing really well' to take her mind off the severity of her injuries.

He realised she was too injured to climb onto the board, so he told her to hold onto a drink bottle holder on the front while he paddled.

'About halfway into shore, she lost consciousness and I had to go grab her by the arm and just keep her head out of the water with one arm and paddle backwards with the other until we got close to shore, where there were lifeguards ready to help.'

Ms Stewart, who has lived in Coogee for several years, swam 50km in November to raise funds for breast cancer research.

'As a breastfeeding mum, I have a whole new appreciation for these incredible organs and want to do my part in supporting the fight against the most common cancer in women,' she wrote on her fundraising page.

The attack has renewed calls for a shark cull around Sydney's beaches, which followed a series of bull shark attacks in January.

NSW Premier Chris Minns said the government was exploring a bull shark cull but would not target great whites, which are protected under Australian law.

'I'm not convinced it would work and we've certainly had no expert evidence suggesting to us that we could ward away great whites from our beaches as a result of a cull,' he said.

'The reality is those sharks may have come from New Zealand or crossed the Pacific Ocean. We haven't received expert evidence or information that a cull would work.'

Coogee Beach was not being monitored by shark surveillance drones at the time of the attack because the area lies beneath a flight path.

However, authorities have since granted a special exemption allowing drones to temporarily monitor shark activity.

The shark that attacked Ms Stewart is believed to have been between three and four metres long.