Peter Dunne, like most Sydneysiders, is tired of the daily grind of commuting — so he's planning a very different way of getting to work.

The 48-year-old father wants to ditch public transport and make the most of the iconic Harbour by swimming to his job.

The long-distance swimmer believes it's an achievable goal and is in the throes of negotiating safety issues — and his wife's approval.

Instead of grabbing his Opal card before leaving his Cremorne Point home, Mr Dunne is aiming to pick up his goggles and waterproof backpack and head down to the water.

He will then swim the 1.5 kilometres across the Harbour, hop out at Mrs Macquarie's Chair on the edge of the Royal Botanic Gardens and walk to work.

Peter and Kate Dunne with nine-month-old Alfie at Cremorne Point. ( ABC News: Mridula Amin )

"The idea came when I realised I wasn't going to make the ferry home, and I looked across and could see where I needed to be and thought, I could be home in 20 minutes if I just swam," he says.

Mr Dunne, a swim teacher, has absolute confidence in his ability to cross the busy waterway, but admits most people think he is nuts.

As he prepares to dive in for this interview, even a passing stranger yells out to him: "Nutter!"

His wife, Kate, says he first told her about the idea when they started dating in 2013 — they married in 2016 — and she has been fighting it ever since.

"He told me, 'I wanna be able to commute to work by swimming', and my first thought was you're going to be fodder for the Manly Ferry ... you are going to be chewed up," she said.

A Roads and Maritime Services (RMS) spokesperson told the ABC that although it was not technically illegal to swim across Sydney Harbour, it was not recommended.

"It could end up causing major issues for ferries and shipping, as a swimmer may present an obstruction to navigation," they said.

"This would be deemed an offence under marine legislation."

Peter Dunne says he's comfortable swimming in the Harbour. ( ABC News: Mridula Amin )

RMS and NSW Police officers have the power to issue a safety direction, or order someone out of the water if it is deemed unsafe.

It is also an offence to enter the Botanic Gardens via the sea wall.

But Mr Dunne considers the plan risk-free and is not fazed about swimming in the Harbour waters.

As a child, he regularly swam from Cremorne Point to Kirribilli to get sausage rolls at the wharf shop, and another pastime was swimming in the wake of ferries with friends.

Mr Dunne says it will be easy to time his commute around passing vessels, and using a fluorescent flotation device will make him stand out.

"You'll be that weird guy all the tourists look and point at," Mrs Dunne says.

But he is concerned about causing any alarm in one of the busiest waterways in the southern hemisphere.

"I would never, ever want to disrupt those operating ships or ferries ... their job is hard enough as it is without some idiot in the water.

"I would really hate to waste someone's time, so that's what stops me."

"That and you might get divorced," his wife adds.

Mr Dunne says he has friends who are skippers and deckhands on ferries but, wisely, he has never discussed his idea with them.