A hidden detail in the background of an otherwise typical family beach photo has divided a local Melbourne community.

In the picture, shared on Facebook on Monday, a man and his young child stand on Carrum Beach in Melbourne’s southeast.

In the background of the photo, what appears to be a dark shark fin glides through the shallow water near a group of two men and a dog.

On Sunday, the Chelsea SES said in a Facebook post that there had been an unconfirmed shark sighting at Chelsea Beach, fuelling speculation a local shark known as “Bruce” had returned.

Chelsea SES on Monday said that following the sighting, it received a message from a family who had been at Carrum Beach on Sunday who, after browsing through photos they had taken that day, noticed the sinister shape in the background.

“Now I have to admit, when I saw the pictures, I wasn’t sure what they were, so I have contacted a number of places to ask their opinions, and they all agree that although they can’t confirm it’s a shark, they can’t say that it’s not,” the Chelsea SES wrote on its Facebook page on Monday.

“The family are very genuine and, in fairness, they’re the first to admit that they’re not sure what they’ve snapped, but they certainly would like to know.”

Nearly 100 locals commented on the photograph.

“I agree that it can’t be discounted – but it’s highly unlikely that a shark cruising in the shallows would not be seen and those in the photo not aware,” one man wrote.

“Looks a bit shallow for a shark with a fin that size,” another wrote.

“Looks like a small shark so maybe that’s why no one was attacked,” one woman wrote.

Chelsea SES and the Victorian Fisheries Authority were contacted by NCA NewsWire.

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