Police rushed onto Southend pier after they received an call reporting that a man was trying to take his own life.
An Environment Agency officer conducting a coastal survey on the mudflats in Southend sparked alarm when he was spotted by a member of the public.
The caller assumed the man, who was walking at the water's edge at low tide, was trying to throw himself into the Thames Estuary.
Police used CCTV cameras to locate the surveyor who was about a mile away from the seafront.
Five officers rushed onto the pier, which was the quickest way to get within earshot of the man, to try to talk to him.
But when they shouted down to him, he shouted back that he was simply doing his job.
PC Steve Adams said: "Someone thought he was trying to throw himself into the estuary, but it was just a chap doing a survey.
"He was walking a long way out along the tide line.
"The call was made to us with good intent.
"The EA hadn't thought to tell us about the work they were doing."
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