It turns out if you'd been anywhere near the Thames waterside over the weekend, you might have seen a very unusual mammal there.
Several users posted on Twitter on Tuesday to show there was a dolphin in the river flowing through London.
Amy Clayfied posted the video on Sunday which shows the telltale fin emerging from the water near Wandsworth.
A couple of hours later, another user posted a follow up video from the side of the river in Hammersmith, showing the marine mammal swimming about.
Dolphins are quite a rarity in the Thames, with there only being one other reported sighting in 2017.
They are not the only unusual sea creatures to appear in the river which flows through the British capital - in 2006, a northern bottlenose whale was seen by the Albert Bridge.