A spokeswoman for East of England ambulance service said it had received “reports of a large number of people suffering from coughing on the seafront in Frinton and Clacton”.
“The cause for this is currently unknown and we and our partner agencies are working to try and establish the cause as quickly as possible,” she said. While we are doing this, we are advising people to not go into the sea.”
She said patients had found their symptoms had improved after coming out of the water. Those affected were advised to wash after leaving the sea, change clothing and drink fresh water, and to call NHS 111 if their symptoms persisted.