The 21-year-old was today still critically ill after being airlifted to hospital yesterday.

He is believed to have jumped into the water next to South Parade Pier, Southsea, which was only 3.5ft deep.

Police were set to interview witnesses today but he is believed to be the latest victim of the 'tombstoning' craze, where thrill-seekers leap into the sea from great heights.

The man was pulled from the water by sunbathers on the beach and staff at the pier, and dozens of emergency services staff rushed in to evacuate the area of beach next to the pier.

About 200 people looked on from behind the police cordon as the ambulance helicopter landed to take the man, who sustained life-threatening injuries, to the specialist neurological unit of Southampton General Hospital.

He was reported to have serious head and spinal injuries and was struggling to breathe.

Police inspector Robert Abel said: 'We've had a few reports of people jumping from the pier and in Old Portsmouth this weekend.

'People should really be aware of the risks involved.'

Sam Britain, of Portsmouth and Southsea Voluntary Lifeguards, who attended the incident, said: 'He was in a very serious condition. We warn a lot of people not to tombstone and this shows how dangerous it can be.

'This should be a warning for people – there is no safe place do it in our area.'

Mary Start, 63, of Balliol Road, Buckland, Portsmouth, was on the beach after the incident at 1.30pm yesterday.

'It's just terrible, people are always being warned about this and it looked like he was in a very serious condition,' she said. 'It really did bring a tear to my eye.'

Anna Evans, 26, of Waverley Grove, Southsea, said: 'I just couldn't believe it. He looked really badly injured when they were taking him away.'

Councillors have previously considered building a pontoon to allow people to jump into the sea safely.

City council leaders are also looking at bringing in a dispersal order for the seafront at Old Portsmouth which would give police doing regular high-visibility patrols along the shore the power to order people to leave the area.

Cllr Paula Riches, executive member for community safety at Portsmouth City Council, said: 'I'm just gobsmacked that this has happened.

'We hadn't though of putting this dispersal order to South Parade pier, but it's certainly something we will look into now.'

>>> Did you see the incident? Call The News on 023 92 545803.