Casuarina Sands, on the Murrumbidgee River, recently claimed the life of a 35-year-old Canberra man, prompting calls for volunteer lifeguards to be in attendance and warning signs to be posted about the risks.

For decades of Canberra's history, the area's beach-like sandy shores and the fresh, brown-green waters have entrenched it as one of Canberra's most attractive cooling-off spots during the summer months.

However, the river remains a dynamic environment with submerged logs and snags moving unseen in the current below the surface, and the shape and depth of the riverbed are constantly changing.

History reminds us there are unseen hazards at Casuarina Sands which have claimed lives for more than 50 years.

Residents of our landlocked national capital have always been eager to seek some cool relief during our hot, dry summers, and our inland rivers and waterways have invariably provided it.

In 1962, under pressure from public demand, it was decided that a concrete weir would be built across the river at Casuarina Sands to partially dam the waters and create a large, artificial swimming lake.

It cost 20,000 pounds to build - a rich sum roughly equivalent to the cost of two average Canberra homes at the time - and by pooling the river flow, expanded the swimming area significantly.

Following its construction, the popularity of the area grew further, drawing hundreds of day-trippers, swimmers, and picnickers to its riverbanks.

However, four years later during a warm day in late November with the river in flood, tragedy struck when three teenage boys all drowned at Casuarina Sands on the same day.

Frank Bree, 18, and Mark Dwyer, 15, both got into difficulties below the weir and when 17-year-old John Lahey went to rescue them, he, too, was trapped in the turbulence. Lahey was hauled from the water and attempts were made to resuscitate him, but he later died in hospital.

An eyewitness report said that a log "came down over the weir and I think it might have hit one of [the boys]".

Such was the extreme force of the tonnes of water pouring over the weir that even an experienced police diver, Constable George Harris, was physically pinned by the current and four other officers had to intervene to rescue him.

Constable Harris was taken to hospital suffering from immersion, shock and bruising.

Two other people were rescued that same day. One of them, nine-year-old Curtin girl Linda Wyllie, was swept toward the weir but hauled to safety just in time, prompting police to issue the public warning. "With the recent floods, the whole bed of the river has changed and is now very dangerous in places."

The death of the three young men at Casuarina Sands reverberated through the community and measures were quickly put in place to warn swimmers.

Lifeguards from the Canberra Life Saving Club began patrolling regularly during the summer months and a warning sign was posted in which swimmers were advised of one of three river conditions: "exercise care", "unsafe" or "prohibited".

Booms and buoys were put in place to define a safe swimming area and other signs prohibited swimming distances upstream and downstream of the weir.

In November 1986, with the river again in flood, 13-year-old Brandon McIlroy was in a small inflatable boat which became trapped in a back-pressure wave created by the weir's turbulence for 90 minutes. The boat developed a leak and the boy started crying out for help.

The incident was witnessed by dozens of people but despite repeated and frantic attempts by a police officer to reach the boy, he was unable to be saved. The boat slowly deflated, the boy was then dragged under and drowned.

The officer received a fractured rib and hypothermia.

Two bravery medals were awarded as a result of actions that day.

The coronial inquiry which followed recommended major safety upgrades to the area. Rocks and concrete were placed below the weir "to create a spillway effect" in an attempt to minimise the turbulence of the water flow.

The following year, the area was closed during the peak swimming season for a full six months while the National Capital Development Commission built a series of steps into the downstream face of the weir to improve its safety. The following year a storage hut was built on the riverbank to store rescue equipment.

Despite the improvements, pressure steadily mounted on the government to find a solution with the weir opponents blaming the structure's location and design, and urging its demolition.

A 36-year-old Narrabundah man died in January 1987 after swinging out from a rope off the riverbank into muddy water.  It again highlighted the issue of undetectable Casuarina Sands hazards because his head hit a rock which was half-a-metre below the surface of the water, but either side of the stump there was two metres of water depth.

As a report was commissioned to assess what should be done, The Canberra Times letters pages overflowed with opinion both for and against, and the debate became fiercely political.

In what was seen as a crucial factor in the government's final decision, a submission from the Australian Federal Police rescue squad stated unequivocally "all members of the rescue squad are in support of the destruction of the weir".

"Not just the lives of those who swim there, but the lives of those who are charged with the responsibility of rescue will continue to be at risk," the police submission said.

The battle of the weir was decided and the concrete structure removed.

In its National Drowning Report for 2018, Royal Lifesaving Australia reported that 249 people drowned across Australia. Three of those deaths occurred in Canberra's inland waterways.

A quarter of those deaths occurred in rivers, creeks or streams and mostly while swimming or other similar forms of water recreation. December and January are notably when most incidents occur.

The ACT has the highest rate of drownings in rivers of anywhere in the country, with the Murrumbidgee ranked third among Australia's deadliest rivers behind the Hawkesbury and the Murray.

The Murrumbidgee now flows freely through Casuarina Sands, its grassy riverbank now lined with barbecues, picnic tables, and amenity blocks.

Deprived with rainfall from its catchment and sluggish under a sun-bleached summer sky, its waters appear safe and placid. But as the most recent drowning shows, the danger posed by unseen hazards and snags still remains.