A happy family photo at the beach became more sinister when people spotted a subtle detail.
The photo, taken of a father and his young child at Carrum Beach in Melbourne, Australia, looks all fine and dandy at first but soon caused some panic when people were sure they could see a shark in the background.
Over on the Facebook page of the Chelsea State Emergency Service (SES) there was a post about a possible shark sighting just off the beach, and they revealed the family who took the photo had been in touch with them.
Hearing that a possible shark sighting had occurred, they checked their holiday snaps and saw what looks like a shark fin poking out of the water.
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With the beach blighted by the occasional appearance of a shark the SES has dubbed 'Bruce', there were worries that it could mean a toothy denizen of the deep was swimming among seaside bathers.
Checking in with the experts, they got an inconclusive response which meant they couldn't say for sure what it was, but it might be a shark, and invited members of the public to suggest what it might be.
People wondered if the news of a shark sighting coupled with the picture with what looks like a fin meant there was a danger of a shark attack at the beach.
Many were convinced that they probably could see a shark, though it would be on the small size if it was due to how close to the shore it had come.
Someone said they'd recently seen some kids 'tormenting a little banjo shark' nearby, suggesting that might be the creature seen in the pic.
Several spotted there was also a dog in the water and took that as a sign that the mystery fin couldn't be a shark as they reckoned a shark wouldn't have been able to resist chomping down on the poor, paddling pooch.
Others wondered how the other people in the photo hadn't spotted the shark if it really was the owner of the fin in the picture.
Even if it does end up being just a little shark they can still be quite dangerous if they give you a bite, even if the idea 'they're more scared of you than you are of them' is supposed to be in play here.
Sharks can be sneaky little blighters when they want to be, and they can silently swim up to unsuspecting bathers having a dip in the sea.
However, even the mighty great white shark has things it must fear in the deep, blue sea as drone footage has revealed that orcas can hunt down and kill the sharks.
Footage from the coast off South Africa showed a pack of five killer whales circling a great white shark before dealing the final blow, and experts reckon the quintet of orcas killed another three great white sharks during the same hunt.
Fortunately, five orcas would be pretty easy to spot lurking in the background of a family photo, unless they're really good at hiding.
Joe Harker