WATCH: 'Massive Shark' Spotted In Sydney Lagoon

What many believe to be a shark fin was spotted in a Sydney lagoon on Monday, just metres from homes and where locals had been kayaking and swimming earlier in the day.

During Sunday's torrential downpour, locals filmed what looked like a large shark fin in Narrabeen Lagoon on Sydney’s northern beaches.

The Instagram user who captured the footage is an Airbnb host in the area, who captioned their video “Great white spotted in Narrabeen Lagoon”.

Large Dorsal fin spotted in Narrabeen Lagoon. Image: Instagram/@itchyfeet1971

The shark sighting website Dorsal Watch posted a report at about 7.30 pm on Sunday.

“[The ] lagoon was opened up to the ocean due to storm and flood warnings,” the report read.



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Dorsal Watch has recorded five other shark sightings on Sydney's beaches this year, with two of them recorded as Great Whites.

Many locals were seen surfing the backwash from the lagoon as it poured into the ocean. People were also seen kayaking and swimming in the lagoon earlier in the day.



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A shark was last spotted in Narrabeen Lagoon in January 2007.

Some residents in Narrabeen had been given evacuation orders throughout the day as torrential rain saw rivers and wetlands overflow.

The Bureau of Meteorology has forecast more severe weather on Monday including heavy rain, strong winds and damaging surf conditions that are likely to further impact the northern beaches.