A swimmer is missing at sea and five others have been taken to hospital after being pulled from the water close to Clacton Pier in Essex.
Emergency services remain at the scene and a major search and rescue is under way to find the male after six people got into difficulty off the coast.
A helicopter has been patrolling the area and police and coastguard services are also attending to help locate the missing swimmer.
Nigel Brown, communications manager for Clacton Pier, told PA the current appeared to have “dragged” a group under the pier.
Staff threw lifebelt rings over the side to help some of those in trouble, he said.
Footage taken by beach-goers from the shore captured the rescue operation about 100 yards from the pier.
Mr Brown said: “Eight of them were in the water but my understanding is four or five got into difficulty.
“My understanding is one person was missing.
“The group that were in the water were very worried about one person they couldn’t see and were saying, ‘There’s one missing’.
“As far as I know, that person’s still missing. They’ve had the helicopter up.”
Mr Brown said it was “difficult to tell their ages” but he believed some were in their late teens to early 20s and fully clothed.
Shop worker Toni Cloke, who had spent the day at the seafront, said police asked beachgoers to clear the beach as emergency services took a number of people away.
The 47-year-old, of Clacton-on-Sea, said: “I saw four or five people get taken in (by emergency services) then we got asked to clear the beach.
“I would say they were holidaymakers.”
EEAS said: “A large response, including four ambulances, our hazardous area response team and the Essex and Herts Air Ambulance, was sent to Clacton Beach this morning following reports of a number of people in difficulty in the water.
“Crews assessed four males and a female patient at the scene before transporting them by road to Colchester Hospital for further assessment and care.”
Essex Police said: “We’re on the scene assisting emergency services colleagues with a serious and ongoing incident close to Clacton Pier.
“There is a significant emergency services presence in the area while the incident is being dealt with. We’ll provide an update as soon as we practically can.”
The Coastguard said it was responding to “a report of multiple people in the water”.
A spokesman said: “HM Coastguard is currently responding to an incident at Clacton Pier following a report of multiple people in the water.
“Clacton beach patrol, the RNLI lifeboat from Clacton and Coastguard rescue teams from Clacton, Walton and Holbrook have been sent to help, as well as the Coastguard rescue helicopter from Lydd.
“Essex Police, Essex Fire Service and Essex Ambulance Service are also attending.
“Five people have been rescued, with the search still ongoing for a sixth man.”