Five people have been pulled from the sea after life rings were thrown to them by pier staff members - but one man is still missing.
Four men and a woman were assessed at the scene before they were taken to Colchester Hospital, ambulance services said.
“There is a significant emergency services presence in the area while the incident is being dealt with.”
A number of emergency responders can be seen searching the water near the pier.
Nigel Brown, spokesperson for Clacton Pier, told the Standard that he heard people calling out and staff ran to the side of the pier where a number of people were in difficulty in the water to the east side of the pier.
“They had been seen going into the water off one of the beaches. It was fairly low tide and as they got deeper around four or five got into difficulty. The currents and tide had taken them towards the pier,” he said.
“A number of staff threw life rings over the side with ropes attached. Two [people] held onto one ring and two others onto two other rings and remained there until Tendring District Council’s Beach Patrol team arrived on a jet ski and Clacton RNLI with two inshore boats.
“They collected the [swimmers] and it was believed from what some members of the group were saying that one person was still missing.”
Mr Brown said he believed the group of around eight to be aged in their teens or early twenties.
The pier was evacuated at the request of the emergency services at 12.20pm.
HM Coastguard is currently responding, as well as Clacton Beach Patrol, the RNLI lifeboat from Clacton and coastguard rescue teams from Clacton, Walton and Holbrook have been sent to help.
The coastguard rescue helicopter from Lydd. Essex Ambulance and fire services are also attending.
Meanwhile in Richmond, police are continuing to search for the body of a missing 14-year-old boy believed to have drowned in the Thames after going for a swim to cool off.
The number of heatwave deaths in open water and off Britain’s coasts rose to at least 11.
It comes after the family of 13-year-old Robert Hattersley said they were “absolutely devastated” after he died when he got into trouble in the River Tyne in Northumberland on Sunday.
Emergency services also confirmed the deaths of a 16-year-old boy in Salford Quays, Greater Manchester, a 16-year-old boy in Bray Lake near Maidenhead, Berkshire, and a 50-year-old man in a reservoir near Leeds in similar circumstances.