Growing up in Canberra, Jacquie Walton heard rumours of eerie and bizarre items lurking beneath the surface of Lake Burley Griffin.

"I've heard about cars and bodies in there," she said.

"Also that people have thrown all kinds of stuff in, so I'm curious to know what's there."

After decades of wondering what could be found at the bottom of the city's lakes, she turned to Curious Canberra for an answer.

I fleetingly considered throwing on some scuba gear and taking the plunge myself, but admittedly I'm not that brave. And Ms Walton assured me that I wasn't alone.

"I'm more than happy to walk around it; I've cycled the lake, walked the lake and paddle-boated," she said.

"But I will not get in the water."

So, I set off to find someone who would.

Divers search for answers

The divers explored a shallow section of the lake, to maximise visibility. ( ABC News: Clare Sibthorpe )

Norm Green and Rowan Jeffs manage a north Canberra dive shop and spend their weekends teaching scuba courses on the NSW south coast.

They occasionally dive in Canberra's lakes to complete construction work or retrieve items that've been lost in the water. But they rarely do it without good reason.

"It's not the Great Barrier Reef," Mr Green joked.

Bearing that in mind, I dipped my toe into the subject by asking about items they'd been approached to salvage in the past. While most were inexpensive, such as tools and toy boats, a diamond or two may be hiding in the murky depths.

"One guy proposed to his girlfriend at the Carillion and after the proposal they had an argument and she threw the ring in," Mr Jeffs said.

The divers found a weight measuring kit and suggested it could have been thrown in by a drug dealer. ( ABC News: Jordan Hayne )

"We didn't even look for that one - it'd be like trying to find a needle in a haystack."

He often refuses to search for small items, given how easily they sink into the soft sediment of the lake bed.

"If I put my hand in, it'll sink to my elbow - so who knows what's buried under there."

This made Ms Walton even more intrigued.

"It adds to the mystery and excitement that there's a whole community revolving around the lake, but what lurks beneath is still unknown," she said.

Sticks and stones that look like bones

Jacquie Walton was thrilled the divers found a window she thought would look great in her garden. ( ABC News: Clare Sibthorpe )

Ms Walton and I watched the divers enter the water, near the National Museum of Australia. In the water, it was an estimated 12 degrees.

After about 20 minutes, the two divers emerged with their hands full.

Mr Jeffs opened a small metal box, with 'Property of the Australian Banks' inscribed on top.

It looked rare and promising.

One diver thought he got lucky when he found this 'Property of the Australian Banks' box. ( ABC News: Clare Sibthorpe )

"I thought I might have found some sort of treasure, but no, just someone's tools," he said disappointingly.

But treasure was found.

Ms Walton's eyes lit up when she saw a window pane featuring a dolphin under Mr Jeffs' arm.

"I'm going to put this near my pond," Ms Walton, a dolphin-lover, said.

The divers organised a clean-up day for the lake, and trolleys, tyres, and old bikes were common finds. ( ABC News: Jordan Hayne )

As well as general rubbish, the divers found a large locked box, a power drill, a brick, silver cutlery, a padlock and a moss-covered bicycle.

"The bike had been there a while," Mr Jeffs said.

"If it was in good [condition] I would have ridden it out of the water."

An unidentified item on the lake's bed. ( ABC News )

During the dive, they found an object that could resemble a human bone.

Knowing that Ms Walton was especially curious about human remains, I turned to the territory's water police.

Sonar equipment uncovers bodies, cars

Sergeant Brett Cunningham is one of the most experienced maritime team members with the Australian Federal Police.

He said police have retrieved about two bodies from Lake Burley Griffin each year, since it was filled in 1964.

Sonar equipment has changed how police search the lake for suspicious items. ( ABC News: Clare Sibthorpe )

"Many moons ago in the late 80s or early 90s, they [police divers] pulled a car out of the lake and my understanding is there were some bones in it," Mr Cunningham said.

In recent years police have been working with new sonar technology, which uses soundwaves to send an image of what lies on the lake bed to a laptop on board the boat.

This equipment has substantially reduced search times and boosted their ability to find items of interest too.

One time, police found five cars submerged in close proximity in a single dive. One was a stolen Valiant car dating back to the 1970s.

"The diver went backwards off the boat and stood up to realise he was on top of a car... so sometimes we do find them by fluke," Sergeant Cunningham said.

Sonar imaging has also uncovered evidence, such as safes, guns, knives, wallets and clothing, which have helped reopen investigations.

An ACT police diver jumps into Lake Burley Griffin. ( ABC News: Clare Sibthorpe )

And despite his wealth of diving experience, even he is occasionally bewildered by what he stumbles across.

"When we did our diving course in '97 we found someone didn't want their floorboards from their house so they dropped them into the lake and we were diving all over them," he said.

"Another time we were diving under Commonwealth Avenue Bridge looking for evidence and people thought it was a good idea to throw those amber construction lights in. We found about 40."

As for Canberra's other lakes, Sergeant Cunningham said there's not much to be found, aside from piles of rubbish and "thousands of shopping trolleys".

Eerily, an old kayak was found at the depths of West Basin. ( ABC News: Jordan Hayne )