Coastguards were expected to begin scaling down their search for a jet-skier today as hopes of finding him alive faded.

The search, involving lifeboats and a helicopter, was continuing but sources said they believed he could have drowned.

The man, believed to be a 21-year-old professional windsurfer, was wearing only a pair of shorts and had no life jacket or wetsuit.

His friend called 999 after seeing him fall from the jet ski off Seaford Bay at 7.30pm yesterday.

It is thought he may have hit his head when he fell.

Coastguards from Newhaven and Birling Gap, along with the helicopter from Lee-on-Solent, Hampshire, joined the Newhaven lifeboat in an extensive search between Seaford Head and Newhaven.

The Newhaven RNLI launched their rigid inflatable lifeboat to help with the search close to shore.

The operation was called off at 11.30pm and resumed this morning at first light but there were no sightings.

Ross Greenhill, of the Maritime and Coastguard Agency, said: "We will be doing a sweep of the coastline and a team will be doing a search from Newhaven to Telscombe but then the search will be called off."

Friends and relatives were on the beach helping with the search. They said the former Seaford Head Community College pupil was a strong swimmer and watersports fan.

The man's jet ski was recovered in Seaford Bay, opposite the Beachcomber pub.

It was taken on board the Newhaven lifeboat as the search was extended to Belle Tout, near Beachy Head.

One searcher said: "He has been missing for so long now that it appears, sadly, we are looking for a body."

Coastguards were expected to issue safety warnings to jet-skiers.

Last year a man broke his back in a collision with a jet ski near Shoreham Harbour.

There was another emergency last summer when a rider-less jet ski was seen going round in circles near Pevensey Bay.

The driver had forgotten to attach his kill cord to the machine, which would have automatically cut the engine when he fell off.