A woman died after she was pulled from the water by Brighton Marina.
Coastguard boats from Brighton and nearby Shoreham were called to the scene as well as police and and ambulance crews.
A coastguard helicopter was also sent from Lee-on-the-Solent in Hampshire and landed on a nearby beach after the alarm was raised at around 4.30pm on Tuesday.
A witness told the Brighton Evening Argus that emergency services performed CPR for “quite a long time” to try and save the woman who was found in the water.
She was taken away on a stretcher by emergency services but her death has since been confirmed.
Police said it is not being treated as suspicious.
A spokesman for the Sussex force said: “Emergency services conducted a search off Brighton beach shortly after 4pm on Tuesday, April 11.
“Sadly, the body of a woman was found.
“Her next of kin have been informed.
“Her death is not being treated as suspicious and a report will be prepared for HM Coroner.”
