Suffolk Police have named a 56-year-old from Redisham in Suffolk as the missing swimmer.
Lawrence Gibbs was last seen at Pakefield, near Lowestoft, at around 5pm on Saturday.
A spokesperson for Suffolk Police said he was seen entering the sea at Pakefield beach, drifting towards Kessingland.
He is described as white, of medium build with grey hair.
He was last seen wearing blue swimming shorts and a swimming cap.
Her Majesty's Coastguard is currently searching for Mr Gibbs supported by Suffolk Lowland Search and Rescue
Police are appealing for help to trace Mr Gibbs.
Anyone who has seen Mr Gibbs or anybody with any information is asked to contact Suffolk police on 101.
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