The RSPCA is appealing for information after a woman allegedly kicked out at a pair of mating swans and an intervening onlooker was pushed into a canal.
The Metropolitan Police are investigating the incident in Limehouse, east London, on Friday.
Footage captured on video and published on Twitter shows the woman climbing down railings and stretching out her leg at the animals in the water.
A group of young people continue to follow the swans around the edge of the canal, before an onlooker carrying a pole tries to intervene.
But while he is remonstrating with the group, a younger man in a blue T-shirt and a baseball cap walks over and shoves the onlooker into the canal.
The man in the baseball cap then flees the scene on a scooter while shouting obscenities at the onlooker, who is still in the water.
The group of young people, including the woman who allegedly kicked out at the swans, then walk away.
In a tweet, the RSPCA said: “We are urging anyone with information about these individuals to contact us on 0300 1234 999.”
Commenting on the video, published by Twitter user @witzhappening, Detective Superintendent Andy Cox tweeted: “Awful viewing.
“Animal cruelty is an indicator of many other vile behaviours and a tendency towards other forms of violence.
“The assault and anti-social behaviour needs our action.”
A spokesman for the Metropolitan Police said on Monday they are investigating the incident and no arrests have been made.
The force said: “At approximately 14:15hrs on Saturday, 27 June, police received a third party report of a man assaulted in Limehouse Basin, E14.
“Enquiries into the incident, including to identify those involved, continue.”
Anyone with information is asked to call police on 101 or tweet @MetCC and quote CAD 4621/27June.