Hampshire Constabulary confirmed that police officers had ordered youngsters to leave the area, as the force sought to combat ongoing issues with tombstoning.
The news comes after a fifth teenager was arrested in connection with the incident involving a gang of up to 100 youngsters yesterday.
The teenager, a 15-year-old boy from Southsea, was arrested on suspicion of assaulting a 20 year old man. He has been released under investigation.
Neighbourhood Inspector Marcus Cator said: ‘We have been aware of anti-social behaviour issues and concerns over public safety in terms of people jumping or tomb stoning into the water at that location over a long period of time.
‘Police and partner agencies are already linked in together to tackle these issues and a lot of work has already taken place.
‘This recurring seasonal challenge is a complex societal issue that can’t be solved by one agency alone.
‘We want to reassure the community that we do take these issues extremely seriously and we will continue to look at how we can make further improvements and carry out enforcement.’
Three young people, a 15-year-old boy, 15-year-old girl and 13-year-old boy, were arrested yesterday.
They have all been released under investigation.