Rescue crews describe the operation to remove him from the icy water
A man has survived despite plunging 180ft (55m) over Niagara Falls and spending 45 minutes in freezing waters resisting his rescuers.
The unnamed man was seen by tourists to scale a wall and leap into the rapids above the falls.
Shortly afterwards he was spotted in the water near the base of the falls clinging to a log.
The man was eventually pulled from the icy waters and taken to hospital with hypothermia and a head injury.
Canadian officials said he was in a critical condition.
A specially trained falls rescue team had rushed to the man's aid after receiving reports of him going over the Horseshoe Falls, one of Niagara's three waterfalls.
However, the man - who was naked - swam away from them toward the middle of the river, police said.
Few people have survived a fall from Niagara
A private helicopter was called in and used the force of its rotor blades to blow him closer to shore.
Firefighter Todd Brunning and another rescue worker then swam about 60 yards, grabbed the man and pulled him to safety, officials said.
Mr Brunning said the man was conscious but unable to talk.
Local resident Phil Richmond, who witnessed the rescue, told The Toronto Star that the man clearly didn't want to be saved.
"It appeared he didn't want to come into shore. I thought he was an idiot to be honest with you," he said.
"It looked like he was swimming, like he was one of those polar bear nuts who swim naked. I didn't realise he had gone over the falls."
It is against Canadian law to go over Niagara Falls, but police would not say if the man would be charged.
Very few people who have been swept over the falls have survived.
In 2003, American tourist Kirk Jones plunged over the Horseshoe Falls in what he claimed was "a spur of the moment act", and lived.
In 1960 a seven-year-old boy also survived the fall after the boat he was in capsized upstream.