A man in his 40s died after being pulled out of the Little Ouse in Thetford, sparking calls for more safety measures in the area.
Police teams pulled the man from the water near the town's riverside complex at 2.40pm on Thursday, however he was pronounced dead on Friday morning.
A Norfolk Police spokesperson said: "Emergency services attended and rescued the man from the water, giving CPR at the scene before he was taken to West Suffolk Hospital. Despite efforts the man, believed to be in his 40s, died earlier this morning.
"The death is currently being treated as unexplained and a post mortem examination will be held in due course.
"As a result of previous police contact, the matter has been referred to the constabulary’s Professional Standards Department."
An East of England Ambulance Service spokesperson said: “A community first responder, two ambulances, a senior paramedic in a support vehicle and the East Anglian Air Ambulance were called to a man who had been pulled from the water on Bridge Street in Thetford just before 3pm yesterday.
"After emergency treatment at the scene, the man was transported by land to West Suffolk General Hospital, with medics from the air ambulance also travelling to provide additional support in his care.”
One witness who did not wish to be named, said: “Air ambulance, land ambulance and police attended to someone pulled out of the river.
“I walked past as the police were arriving and started CPR efforts until the ambulance and air ambulance arrived sometime later."
Clare Higson from Thetford River Group said they had long called for safety measures to be put up at the river, including railings, a buoyancy aid or a throw line.
The group's founder Sean Ready was out on the river at the time, however did not witness the incident.
He said: “We were just about to go around Butten Island and for some reason we just didn’t.
“It must have been a minute or two after we went down stream and the guy was in the water.
“Later on, we found a member of the public who knew more than we did.
“There was a guy in the water and members of the public managed to get him out, they went to the gym and got a defib then along came the medical services and the police.
“They tried to resuscitate him."
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