大象传媒

Video footage, taken on the 22nd July, shows what appears to be a fin moving through the water near Hammersmith Bridge.

The Port of London Authority said the Thames had an "abundance of aquatic life with occasional visits from dolphins, porpoises and even whales".

But, it said it was "unlikely that any sharks would swim that far upstream".

So what could the fin belong to? And even if this isn't a shark, could they be found in the Thames?

大象传媒 Radio London's Shay Kaur Grewal has been finding out.

(Image credit: Jam Press / @CharlotteWebb / Getty Images)