This is the moment a man was pushed into a canal in east London canal after apparently trying to defend mating swans from a group of youngsters.
In a video circulating on social media, the group are seen gathering at Limehouse Basin, before one girl approaches the swans and appears to kick at the pair of animals.
A man with a stick then approaches the group and appears to confront them.
But a boy with a backpack and a cap then runs towards him and shoves him into the canal.
He then rides away on a scooter and shouts "have that".
Metropolitan Police Superintendent Andy Cox condemned the "vile behaviour" as he urged people to come forward and give information about the incident, believed to have taken place on Saturday.
He said on Twitter: "Awful viewing. Animal cruelty is an indicator of many other vile behaviours and a tendency towards other forms of violence.
"The assault & anti social behaviour needs our action. Help us by letting us know who these offenders are via 101; @MetCC or confidentially via Crimestoppers."
The RSPCA has also launched an investigation into the incident.
The animal welfare charity tweeted: "If anyone has further information on these individuals, please contact us on 0300 1234 999".
Twitter users have reacted to the footage.
One person said on social media: "There is NO excuse for this behaviour. You know where this leads if not punished and that swan could die from its injuries elsewhere."
Others suggested the girl was trying to separate the swans from "attacking each other".
"It looked like the girl was trying to stop one swan from trying to kill the other one - as they often do at this time of the year," one said.
He added: "The kid who pushed the bloke in needs to be found and charged though!"
A Metropolitan Police spokesperson told the Evening Standard no arrests have been made but enquiries into the incident, including to identify those involved, are ongoing.
"At approximately 14:15hrs on Saturday, 27 June police received a third party report of a man assaulted in Limehouse Basin, E14," said the spokesperson