The boy is believed to come from the local area and has not yet been named. He is said to have been in the sea just after 4pm this afternoon with a friend when he disappeared.
Sussex Police began searching their area assisted by the local coastguard and other emergency services around the West Beach area of Newhaven.
More top news
Kate Haskell has the weather for the east of the region
Kate Haskell has the weather for the west of the region
Police said they are concerned for the welfare of 13-year-old Serena Alexander-Benson.