Nine students from the University of York have been temporarily banned from the city centre.
Police issued with dispersal orders banning them from the heart of the city for 48 hours.
It follows calls from the public that people were in the River Ouse. Some of them were floating on lilos and other inflatables.
The city centre police tweeted: “The River Ouse is a dangerous river and has taken too many lives.”
A North Yorkshire Police spokeswoman told the Press:
It goes without saying that this was a very dangerous act and could have ended in tragedy.
We do not want to be killjoys, but the river is extremely dangerous, especially when alcohol is involved.
We strongly advise people to not enter the river and never, ever go on the river in lilos.