A search and rescue operation is began this morning after reports of a man in the water at Brighton Marina.
A spokesman for Sussex Police said: "Sussex Police were notified to a person in the water. Officers attended but unfortunately there was no sign of someone who could be rescued."
The spokesman added that they were being supported by colleagues from East Sussex Fire and Rescue Service, Coastguard and South East Coast Ambulance Service in carrying out the search and rescue.
Shoreham Coastguard also attended. A message posted on the HM Coastguard Shoreham Facebook page read: "00:45 20:02:2019 Team paged with Newhaven Coastguard RNLI Brighton and Coastguard Helicopter, to report of male in the water. An extensive search was conducted with SECAmbHart, EastSussexFRS and Sussex Police.
"Amazing dedication and teamwork from all services involved."