A spokesman for Norfolk Police said:
"The man was retrieved from the water and was taken to Addenbrooke's Hospital by air ambulance for treatment. He is currently described as being in a critical condition.
"Police and the Health and Safety Executive are carrying out a joint investigation into the incident."
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Mostly dry this morning but cloud will increase through the day with rain arriving tonight.
A mostly dry night with some clear skies allowing a touch of frost to form in places. Increasing cloud from the west tomorrow.
A woman from Milton Keynes who became Britain's first surrogate 30 years ago says she still wonders what became of the baby she gave away.