The man-made Lake Burley Griffin is the watery centrepiece of the national capital, splitting Canberra into north and south. But a walk around its shores reveals the lake not only separates the city geographically, but also by (quite fierce) opinion.

Key points: Lake Burley Griffin is closed periodically due to blue-green algae

Lake Burley Griffin is closed periodically due to blue-green algae The stigma that the lake is dirty is keeping some Canberrans from taking a dip

The stigma that the lake is dirty is keeping some Canberrans from taking a dip Experts say the water is safe, and provides nice relief from the heat

The National Capital Authority (NCA), which manages the lake, conducts water safety tests regularly and erects signs to give a green or red light to swimming.

Previous summers have seen swimming closures due to bacteria infestation, leaving people frolicking on and around the lake, but not so much in it.

Canberrans are rushing to Lake Burley Griffin to seek some relief from the recent heatwave. ( ABC News: Clare Sibthorpe )

For some Canberrans, the lingering childhood memories of seeing blue-algae warning signs by the water overpowers the NCA's approval that the lake is safe.

Rumours its depths hold everything from dead bodies to shopping trolleys probably also do not help.

But the growing number of residents seen splashing in the lake in recent weeks shows perceptions are changing — and it is not just thanks to the oppressive post-Christmas heat.

'Better than pools'

A lingering stigma that the lake is "dirty" or "filled with blue-green algae" prevents many Canberrans from taking a dip. ( ABC News: Clare Sibthorpe )

Anthony Brown has lived in Canberra for a decade, but first swam in Lake Burley Griffin last year after his son Jackson raved about how refreshing it was.

He said he used to swim only in the Murrumbidgee River because he preferred flowing water, and did not think you could swim in the lake because of blue-green algae.

"But now that I know it's safe I like it better than pools," he said.

"I just think that lots of other people won't swim here because they still have it in their minds that it's closed … there just needs to be more signs that it's safe."

Zenia Anderson, who swims in the lake twice a week, agreed that it was nicer than public pools, with the bonus of being free.

She said the water was gorgeous, despite occassionally being "pond-scummy" — though she always checked the water safety tests before getting in.

"And we're that far away from the beach that I'll literally take whatever I can get," she joked.

The lake has swimming spots with safety barriers for children. ( ABC News: Toby Hunt )

She found it was usually longtime Canberrans who did not share her lake love, including colleagues who "scrunched up their faces" when she revealed the location for her post-work dip.

"Definitely the people who have been here for five or 10 years are most outraged when you're new to town and you're willing to dunk your head under the water," she said.

"But I'm on a crusade to convince people that it's totally fine."

Avoidance due to paranoia, swimmer says

Despite growing up in the city, James had never even heard of the closures due to algae.

"People ask me if they can swim in the water, and I say, 'well of course', and they say, 'really?'"

"I just think people are a bit paranoid about this stuff nowadays."

His 12-year-old daughter Jess and her friend Ava enjoy the water so much, they often swam out to the island near Black Mountain Peninsula, on which they built wooden huts with their friends last summer.

Jessica Turvey and Ava Warden enjoy swimming out to the island near Black Mountain Peninsula. ( ABC News: Clare Sibthorpe )

'Only if I was pushed'

But despite the praise of some, for other Canberrans the old-time debate has not quite yet died.

"The only way I'd ever end up in Lake Burley Griffin is if I was pushed," one man said, braving a walk around the shore in 40-degree heat.

Another person noted that the blue-green algae blooms could irritate skin and make people ill, and said he did not feel confident enough in the NCA's water rating, given the lake's persistent murky colour and not-so-nice smell.

But the NCA's project officer for lakes and dams, Michelle Jeffrey, said there was almost always somewhere to swim in Lake Burley Griffin, and urged residents to use their Swim Guide App to learn where to find the best swimming spots based on water quality.

"People have these memories of the lake being closed, but they're not getting the message that we're actually open the majority of the season," she told ABC Radio Canberra.

"We actually test in 10 different locations around the lake, so that gives you really great confidence that the water is monitored really well."

Lake Burley Griffin is becoming a more popular swimming spot for families. ( ABC News: Clare Sibthorpe )

Water science expert Associate Professor Fiona Dyer said there was a misconception that the lake's dark colour and at times foul smell, meant it was unsafe to swim in, when in fact it was "most often" safe.

"When you look at the lake's brown colour, that's not necessarily algae, some of that is fine sediment. So things that have washed off the urban area we live in," the University of Canberra researcher said.

"Some of what is in the water is actually algae, but the NCA tests that very regularly. If it is toxic algae — not all algae is toxic — they close the lake. In terms of smells, there are many things that could cause the water to smell.

"I just don't swim in the lake after one of the heavy rainfalls because lots of bacteria gets washed up in the lake. But the smell is not just from algae."

She said the ACT Government could do more to help water quality, such as more regularly cleaning gross pollutant traps and wetlands, but stressed it was restricted in available funds and resources.

Canberrans must also take some responsibility, she said, by keeping their stormwater drains clean.

Water rats should excite, not deter swimmers: professor

Families who did not head to the coast for summer have been flocking to Lake Burley Griffin. ( ABC News: Toby Hunt )

Associate Professor Dyer agreed with the sentiment that swimming in Lake Burley Griffin and other lakes was more pleasurable than a dip in Canberra's pools.

"I sometimes tell people we are quite happy to swim in swimming pools with chemicals, which kill living organisms, but yet you, as a living organism, get into that," she said.

"Yes, they might not like that the lake is brown and you can't see the bottom, and they're worried about the ribbon weed touching their skin as it's slimy … but that's not dangerous at all."

She even did not mind swimming amongst the water rats that were often seen bopping in Canberra's lakes — particularly in Lake Ginninderra.

"Water rats have a bad name but they're a native … I prefer to call them Rakali. It's not an an indication of really poor water quality," she said.

"They're a fabulous native animal that lives in our lakes and we should be pretty excited by them."

In fact, she said she would be happy to swim next to them — even if she was not pushed in.