Recent floods bought the biggest inflows into Lake Burley Griffin in a decade, with trees, debris and stormwater washing down with it.

The stormwater is responsible for the smell.

Tony Le Mesurier and Jeff Koehler are responsible for the trees, debris, dead animals, trollies, bikes and electric scooters swimming in the stormwater.

Of course, not all of that has washed downstream from Jerrabomberra or Molonglo.

Neuron and Beam were chosen as ACT's scooter providers in 2020, purchasing permits to operate a combined 1800 vehicles on Canberra's paths and roads.

Mr Koehler has been hopping aboard the old oyster punt responsible for plucking pollutants from the lake since well before the shared-scooter scheme took off.

He said the glow of orange or purple below the surface has become relatively common since then.

"There's a lot," he said. "We'll pluck them out and put them on the shore. The problem is people throwing them back in again.

"I once picked the same scooter up three days in a row. They're quite heavy too."

A no-parking zone has been introduced around Lake Burley Griffin to stop them ending up in the drink, a prevention method now rolled out in other cities.

As users log in to use scooters with their mobile phones, identifying "anyone behaving irresponsibly" is relatively easy. A three-strikes-and-out rule means riders found to flout the rules are barred from scooter travel.

"Thankfully, cases of vandalism and dumping are rare," a Neuron spokesperson said.

The decision to provide Beam and Neuron with the rights to Canberra's roads was made carefully, particularly given the well-documented misadventures of electric bike hire down south, with Melbourne City Council driving Singapore's oBike scheme out of town after declaring the dumped bikes an environmental hazard.

A Beam spokeswoman said the industry had learned a lot from the failure of bike sharing.

"It has developed robust anti-vandalism technologies and strategies to prevent such anti-social problems before they occur," she said.

"Should they happen, we investigate them all and work closely with the police to identify the culprit and enforce safe use of e-scooters to ensure that the actions of a few don't ruin a good experience for others.

"We definitely hold them accountable for their actions, including financial penalties and a permanent ban from our platform. They are also referred to the police for potential further action."

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Unfortunately, electric scooters are far from the only workplace hazard for the crew tasked with pushing the oyster punt out before sunrise from Yarralumla Bay.

Barely visible rowers in the morning mist are a unique challenge, Mr Koehler said.

"It's like playing Frogger," he said, referring to the old arcade game.

"A horn would be good."

The oyster punt crew aren't the only ones plucking foreign objects out of Lake Burley Griffin. The Australian Federal Police, which runs training exercises in the lake, have sent divers to investigate suspicious items below the surface a number of times over the years.

Both sad and sinister objects have been recovered; boats and cars submerged for decades, drugs, weapons and even fireworks have shown up.

During a 2016 drought, boat users reported striking something below the surface around the Monaro Highway underpass. The dive team searched the area, discovering five stolen cars stacked in a pyramid, pushed off a nearby boat ramp and drifting to the same spot before sinking.

Shopping trollies, bikes and scooters are much more common, an AFP spokesperson said.

David Wright, National Capital Authority lake and dam manager, said divers once brought up an old newspaper stand near the dam, presumably dragged from the city.

He said while it's a bit of a mystery what lays in the depths, wheelie bins and shopping trollies are common near the shoreline.

The Australian National University rowing team just pulled about 10 carts and a couch out of Sullivans Creek, he said.

Scooter users aren't the only Canberrans misbehaving around the lake either, with paddle borders reportedly taking the opportunity for a tow when Balloon Spectacular comes to town, holding onto ropes dangling from balloons as they pass overhead.

Dodging boats was higher risk during the pandemic, with demand for licenses surging as Canberrans, presumably longing for the South Coast, took to the water.

The aftermath of the recent floods has seen 140 tonnes of debris pulled from the lake so far, around 60 per cent of which can be recycled by Corkhill Bros at the tip. The rest is "too silty" not to become waste.

Typically, the north-westerly winds blow debris into the lake, where it piles up around the Jerrabomberra wetlands. While some of the logs make good habitat, the rubbish stacks up amongst the sticks and trees, meaning the clean-up has to be done by hand.

Mr Wright said big flows from heavy rain tend to bring more nutrients into the lake which settle down to the sediment.

"Although immediately with the wet weather it tends to disrupt the growth of algae, in later years we might see that algae come back because of the nutrients that have flowed in," he said.

Mr Wright said the ecological health, water quality and recreational health of the lake are all somewhat dependent on what happens in the catchment.

"One of the biggest challenges that we face in the continued health of the lake will be how the catchment is managed to reduce pollution and excess nutrients," he said.

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