Emergency services believed to be searching for missing person in water near Clacton Pier
Police are dealing with a "serious and ongoing incident"
The incident comes as Britain is hit by the hottest day on record, with the temperature reaching 39.1C in Charlwood, Surrey.
Essex Police said in a statement: "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."
HM Coastguard has now confirmed that three swimmers have now been rescued from the water around Clacton Pier in Essex.
A major search operation is under way to try to find a fourth missing swimmer.