A man in his 50s has died, and another in his 20s was resuscitated, after they got into difficulty in the water at Sea Palling.
Two other people were assessed by paramedics at the scene, but did not need to be taken to hospital.
Helicopters, lifeboats, coastguards, lifeguards, paramedics, firefighters and police were all sent to the scene following multiple 999 calls at about 11.30am.
Liz Hustler, of HM Coastguard, said they were told four people were in trouble in the sea off Sea Palling.
She said two of them got to the shore without help, and two others were helped from the water by members of the public after they were caught in a rip tide between two sandbanks in a stretch of the beach not patrolled by lifeguards.
Two RNLI lifeguards were on the shoreline within the area patrolled by the team when they were alerted by a colleague in their tower above to an incident in the next bay, some 800m away.
The pair on the beach rushed to the scene and found a 54-year-old man and a 26-year-old man had been helped from the sea by members of the public and were not breathing.
A further two males – a 16-year-old boy and a man in his 20s – had left the water by themselves.
Jack Hood, RNLI lifeguard supervisor said: 'It was an extremely busy scene with lots of people around, but it appears these four men got into distress in the water because of one of the notorious rips that can occur off this coast.
'One of our lifeguards immediately started CPR on the 54-year-old, assisted by a member of the public who declared he was a medic. Meanwhile, a member of the public who had experience of first aid was giving CPR to the 26-year-old, so our lifeguard moved her focus to take over his treatment.
'In the meantime, our other lifeguard had rushed to obtain oxygen and a defibrillator from the RNLI's beach lifeguard unit. Whilst the 26-year-old was breathing when she returned with the equipment, the 54-year-old was not. Both RNLI lifeguards attempted to use the defibrillator on the older casualty, but the unit detected that no shock was able to be administered. Unfortunately, he was pronounced dead at the scene by air ambulance service personnel.'
The 26-year-old was taken to the Norfolk and Norwich University Hospital by air ambulance and the two swimmers who had got out of the water by themselves were thoroughly assessed and advised to seek medical help should they feel ill at any point later in the day. Both declined to go to hospital.
Mr Hood said: 'This is an awful, tragic outcome, and our thoughts and prayers are with the family and friends of the older man. For a seemingly innocent swim in the sea on a hot day to turn into a tragedy like this is a heart-breaking thing for anyone to deal with.
'We would remind anyone who is visiting the beach to be aware of the tides and the conditions, and wherever possible and practical, to swim at a lifeguarded beach. The RNLI's lifeguards and lifeboat volunteers do everything in their power to assist and rescue people in distress, but this awful incident just goes to show the unpredictability and the potential danger of the sea.'
One bystander, who saw the aftermath of the rescue, said: 'I just heard siren after siren after siren.
'As we got there, there was a helicopter coming in to land at the beach. There were two search and rescue helicopters. The lifeguard boat was in the water and there was the RNLI lifeguard down there, and the coastguard.
'[I saw] two casualties. One of them was completely horizontal and the other was sitting up. They were there about 20 minutes and they then stretchered one of the casualties into one of the yellow helicopters and it went off.
'There were a few folk around the edge who were obviously very concerned and quite upset. But some people thought it was a drill.
'I do hope that the one they carried off was alright.
'I have to say, it was a pretty sombre mood as they were carried into the helicopter. It did not feel particularly good.'
Lloyd Gladding, who lives on Beach Road in Sea Palling, said he went to the beach after hearing the sirens.
He said: 'As the first helicopter came, the lifeguard crew made people stand a fair distance back. They shut the beach off a little.
'You could see a person lying in the floor. The first crew came up and people were trying to best to save people. There were a lot of people there.'
He said it was common knowledge among villagers that there were dangerous currents and under currents around the reefs, and while there had been other rescues in the nine years he has lived in the village, they were often of divers, and had never been as serious as this.
He added: 'A lot of people in the village are shook up. A lot of people are worried.'
A coastguard helicopter from Humberside, coastguards from Happisburgh, Mundesley and Winterton, Happisburgh's two lifeboats and lifeboats from Mundesley and Hemsby were all deployed.
Twitter user @DjRemedee wrote: 'Never seen so many emergency response vehicles in my life, coast road to sea palling , stay safe out there.'
One crew of firefighters, from Stalham, and another fire service officer, also attended.
Did you see what happened? Contact alex.hurrell@archant.co.uk or martin.george@archant.co.uk or call 01603 772468.
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