After almost three decades of pulling murder weapons, rusted cars and decomposed bodies from its depths, the veteran police diver instead sees the dangers that lie within the vast stretch of water.

You would be hard-pressed to find a Canberran who has spent more time beneath the lake's surface, or one who is so well-attuned to the lake's role in some of the capital's most notorious crimes and tragedies.

Sergeant Le Lievre began as a police diver on Lake Burley Griffin with ACT Policing in 1979.

He is now part of the AFP Specialist Response Group monitoring the lake from Yarralumla Water Police base.

Sergeant Le Lievre said he knew intimate parts of the waterway no-one else had seen.

"That gives you a different dimension and a different aspect to Lake Burley Griffin, because people don't see what's underneath it," he said.

"We know what's underneath it."

He said the lake was a common dumping ground for stolen cars, evidence from crimes such as firearms or safes, and bodies of people who had died or taken their life.

Sergeant Le Lievre said he had plucked about 15 lifeless bodies from the lake over the years.

"It's part of the job, like anything else that's a bit untasteful to the general public," he said.

"After a while you get certainly insulated and you just have that typical copper attitude - job to do, we'll get on with it."

One of his clearest memories is the fruitless police search for the gun used to assassinate ACT police chief Colin Stanley Winchester in 1989.

More than 10 police divers spent three months scouring water about 20 metres out along the lake's perimeter.

"We basically searched the whole lake. Not quite, but certainly a large majority of the lake."

The weapon used in the high-profile killing has never been found.

He was also among divers who trawled the lake's floor for five days looking for flying debris after the Royal Canberra Hospital implosion in July, 1997.

Police scrutinised video footage of the blast for splashes which indicated where schrapnel from the impact fell in the water.

They recovered more than 50 chunks of metal which ranged from schrapnel the size of a 50 cent coin, to a piece of metal the size of a car bonnet which weighed more than 20 kilograms and landed in water 760 metres from the site.

It was another stroke of luck which saw Canberra's water police play a pivotal role in one of the country's most shocking killings.

Sergeant Le Lievre was in charge of a team tasked with a near impossible mission - to scour the murky depths of the lake for two small knives used in the murder of Bega schoolgirls Lauren Barry, 14, and Nichole Collins, 16.

Leslie Camilleri and his companion Lindsay Beckett abducted the girls before they raped, tortured and stabbed them to death in October, 1997.

The two men were on their way through Canberra when they stopped and hurled the murder weapons from the Commonwealth Bridge into the lake below.

A police tip-off led divers to the water beneath the bridge and the first diver had plunged in.

He surfaced soon after, grasping one of the knives.

That weapon proved to be a vital piece of evidence in the case against Camilleri and Beckett, who were convicted and sentenced to life in jail.