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Emergency services conducted a search of the River Medway after reports of a man jumping from Rochester Bridge.
Police, lifeboat and coastguard crews scoured the water for three hours after being called just after midnight, but found nothing.
The report was later confirmed as false.
Efforts continued until information was received that it was a potential hoax call.
During the search, the teams' attentions were diverted by shouts of "help" from across the river, which were revealed to be fake after an extensive search.
Crews were stood down shortly after 3am.
Police spokesman Jon Green said: "Police were called just before midnight by a man who claimed he saw someone jump from Rochester Bridge.
"Police attended along with coastguards and a search was carried out by boat and helicopter. On making further enquiries it transpired that the caller had not seen a man jump and the search was called off."
The Medway and Sheppey Coastguard Rescue Teams, who are volunteers, have reminded residents that hoax calls are not what they volunteer for.
Police are investigating the original call.