The lifeboat was sent out yesterday afternoon after a fishing boat discovered a body in the fishing lane four miles offshore.
The RNLI collected the body and brought it back to Sovereign Harbour, where it was handed over to the police.
An RNLI spokesman said it had likely been at sea for some time.
A spokesman for Sussex Police said police were alerted by HM Coastguard reporting there was a body floating out at sea just before 4pm.
The individual has not been identified and enquiries are ongoing, the spokesman added.
The incident is not being treated as suspicious and the coroner’s officer has been informed.