Social media users were baffled on Tuesday when pictures emerged online of what appeared to be a shark fin in the River Thames in front of the London Eye and Houses of Parliament.
One social media user who shared a picture said on Twitter: "Walked through central today and looked in the river.. is that a shark in the thames??!"
walked through central today and looked in the river.. is that a shark in the thames??! pic.twitter.com/JGlj4O5ibf— Yasmin Dan (@YasminDan)July 14, 2020
Another picture of a grey fin cutting through the Thames in Hammersmith caused further speculation on social media.
"Wow you can clearly see its fin #riverthamesshark," said one Twitter user in response to the pictures.
Others were quick to cotton on that there was something not quite right with the images.
"It's fake," said one Twitter user in response to the pictures.
NAHHHH ‼️‼️ this was by Hammersmith not long ago 😳 pic.twitter.com/bgTOsbCiV2— Cam (@CamTopicalJuice)July 14, 2020
However Martin Garside from Port London Authority told the Evening Standard a young man admitted the images were part of a hoax organised by him and his friends.
"He phoned us late last night to say it was photoshop," said Mr Garside.
"He said he was trying to hoax the media and called to apologise that it took up some of our time."
Mr Garside explained that the prank was "pointless" as sharks and harbour porpoises have been spotted in the River Thames before.
"It's a bit juvenile as we do get sharks in the River Thames, mainly in the Thames Estuary - though it is unusual," said Mr Garside.
"But if you see a fin like that, we get them all the time. If it's a dorsal fin it's most likely a harbour porpoise."
It comes after a humpback whale was spotted in the River Thames in October last year.
Multiple sightings of the 26ft mammal were initially reported between Rainham and Greenhithe in Kent and some enthusiasts even managed to capture the creature on camera.