The emergency services were called to reports that a man had entered the water in Bognor on Sunday evening.
The Selsey Coastguard team and RNLI crew responded to the call from Sussex Police at 9.12pm (Sunday, September 1).
The lifeboat sped towards Barn rocks off Aldwick to start a search to the east as far as Felpham, as at first police could not confirm where the man had entered the water, a Selsey RNLI spokesman said.
Searches were also carried on the beaches.
The lifeboat continued searching at sea and had completed three legs when, just before 11.00pm, the man was found by one of the teams, the spokesman said.
The Selsey Coastguard said: "Thankfully we located the missing person on the beach and provided casualty care until the police arrived, the casualty was then left in the care of Sussex Police."
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