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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Dry with warm sunny spells for most after a cloudy start in some areas
Two men have been stabbed in attacks in Luton town centre. Police have closed off two roads while they investigate the crimes.
It may start cloudy near coasts but the sun should break through, especially in the West.