Emergency services were called to a river on the outskirts of Norwich.
The Coastguard and ambulance service were dispatched on Tuesday evening to Yarmouth Road by the Rivergarden in Thorpe St Andrew.
A spokesman for the coastguard said two teams were sent to attend to a man.
Police were also called to assist, but a spokeswoman said it was ambulance-led.
The River Yare runs through Thorpe St Andrew, and is a popular destination for sunseekers during hot weather.
Ian Mackie, Thorpe St Andrew county and district councillor, said he had spoken to a member of the Coastguard who told him a man had been taken unwell on the island, and is now sat in the ambulance recovering.
A fire officer had earlier been on the scene around lunchtime to give safety advice.
It comes after Coastguard and RNLI teams from Wells were called to a dramatic rescue after a man had got into difficulty in the channel at Burnham Overy Staithe on Monday around 5.20pm.
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