Fears great white shark is lurking in flooded Sydney lagoon

There are fears a great white shark has entered a flooded Sydney lagoon as footage emerged of what some reported as a fin lurking in the murky water.

The video, filmed at Narrabeen on Sydney’s northern beaches, circulated on social media after heavy rain flooded the area over the weekend, causing many residents to be evacuated on Sunday night.

A fin-like object can be seen in the video bobbing in the water from a distance, sparking concerns rising levels of the lagoon caused a shark to spill into it.

Dorsal, a global shark reporting and alert app, reported there had been a great white sighting from the shore in North Narrabeen on Sunday.

“Great white spotted in Narrabeen Lagoon. Fin spotted from shore. Lagoon was opened up to the ocean due to storm and flood warnings,” an alert on the dorsal website said.

A number of people on social media were terrified, with one comparing it to scenes from “Sharknado”.

“That’s a bit scary,” one said on Facebook.

“Narrabeen is being evacuated as it’s flooding so if it is a shark it’s going to (be) like a scene of Sharknado,” another commented.

But many doubted it was actually a shark, with some suggesting it was just a log.

“It was a log. It floated past our house. We thought it was a shark at first,” one woman commented.

“I saw the video. It bobs like a log in one spot. Definitely not a shark,” another claimed.

A NSW Department of Primary Industries spokesperson told Yahoo News Australia it is “unable to identify the object in the water as a shark”.

“NSWDPI advises ocean goers to be SharkSmart with heavy rain making ocean conditions turbid and murky,” the spokesperson said.

A Northern Beaches Council spokesman told Yahoo News Australia it was taking every possible precaution following speculation about the recent shark sighting.

“A jet ski has been sent out in an attempt to locate the shark and signage has been erected,” he said.

“At this stage, council is unable to confirm the presence of a shark.”

Sydney receives heaviest rainfall in up to two decades

The Sydney basin has been pummelled over the weekend with the heaviest rainfall in up to two decades as NSW communities fell prey to an east coast low that also brought strong winds.

The deluge is not yet over, with forecasters warning more rain will fall in Sydney, while further south along the NSW coast residents are bracing for damaging winds and heavy falls.

Sydney, the Central Coast and the Blue Mountains were soaked after receiving between 200mm and 400mm of rain from 9am Friday to 5pm Sunday.

The last time Sydney and the state's coast had as much rain was in mid-2016.

"But we've surpassed those figures and you have to go back, as far back as 1998, to see totals like we'll get," a bureau spokeswoman said on Sunday.

Four people were hospitalised on Sunday afternoon after a tree fell on their car in the Sydney CBD, and a 16-year-old boy was treated for broken ribs after being trapped between debris in the Hunter's Allyn River.

A car was also reportedly swept away in Galston, in Sydney’s northwest, on Sunday afternoon but police have no evidence anyone was inside the vehicle.

There was relief on Monday when floodwaters along major rivers appeared to peak overnight. However moderate flooding has persisted at North Richmond and Windsor along the Hawkesbury River, as well as Menangle on the Nepean.

Water from the Georges River was also inundating Milperra and Liverpool in western Sydney early on Monday, the NSW State Emergency Service said.

River levels at Milperra are now higher than during the 1988 flood and major flooding is impacting other areas such as Warwick Farm and Chipping Norton.

Residents near the Narrabeen Lagoon in northern Sydney evacuated overnight after warnings of significant flooding.

More severe weather conditions forecast

The Bureau of Meteorology has forecast more severe weather conditions on Monday with heavy rains, strong winds and damaging surf possible along the entirety of the NSW coast and inland southern NSW.

Utility companies are rushing to restore power in swamped regions, with more than 110,000 Ausgrid customers – primarily in northern Sydney and the NSW Central Coast – without power on Monday morning.

"The strong rains and wind have caused more than 3000 hazards to the electricity network such as fallen power poles, large trees across roads, damaged wires and extensive flash flooding," Ausgrid said in a statement.

Endeavour Energy has more than 19,000 customers without power.

The NSW SES has responded to about 10,000 calls for help and carried out multiple rescues of people trapped by rising rivers and floodwaters.

"People need to be reminded – if you can't see the road, don't drive across it," NSW Emergency Services Minister David Elliott told the Seven Network.

The weather has also caused major disruptions to Sydney's public transport system and road networks, with commuters told to check timetables and travel apps before setting out on Monday morning.

Some train services and harbour ferry services have been cancelled.

Sydney's dams are filling up with Warragamba dam now at more than 60 per cent capacity after jumping from around 45 per cent last week.

With AAP

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