The kayaker was wrapped in blankets and shivering with cold when approached by the Otago Daily Times last night and said he was "not with it" to talk.
He then told St John ambulance officers his name was Bruce Paige and he was 70.
The Clutha River was flowing at 647.3cumecs in the upper reaches near the Cardrona River confluence yesterday afternoon, exceeding the first flood level warning of 600cumecs.
The Otago Regional Council had placed a high alert warning on its water information website.
Mr Spencer Bower, of Wanaka Helicopters, was asked by Wanaka police yesterday to search the river after the police southern communications centre received a 111 call about 4.30pm that a kayaker was in trouble.
The man was reported to be already in the water and clinging to his kayak as he went under the red bridge at Luggate Red.
Mr Spencer Bower flew over the river and found Mr Paige still clinging to his kayak 4km-5km downstream of the bridge.
He dangled a rope from his helicopter to Mr Paige and then eased him to the shore.
A boat from Lakeland Adventures retrieved the kayak while Mr Spencer-Bower flew Mr Paige to Wanaka, where he was transferred by ambulance to the Wanaka Medical Centre for treatment.
"I thought he was gone. I didn't think he would last much longer. He was very, very lucky," Mr Spencer Bower said.
Mr Spencer Bower said Mr Paige had said he thought he was going to have to float all the way down to Lake Dunstan.
Senior Sergeant Alan Grindell said last night the kayaker was wearing a wetsuit and a lifejacket.
Apart from being cold, he was uninjured.
Wanaka swift water rescue team member Roy Bailey said last night the kayaker was lucky someone had seen him going under the bridge.
"The golden rule is don't kayak alone."
Mr Bailey said it was the wrong time to kayak the Clutha River.
It was particularly high and flowing very fast with water right up into the willow trees lining the banks.
