Kirk Jones, 40, of Canton, Michigan, is the first person known to have plunged over the falls without safety devices and lived. He could be fined $10,000.
"It was an impulsive one-second thing and in a second-and-a-half I was in the water," Jones said Tuesday in a telephone interview with a Detroit television station.
"I was in the water for about eight seconds," the out-of-work shipping and receiving clerk said. "I was immediately enveloped by what seemed like tons of water."
Family and friends said Jones had been considering the stunt for years — but more so in recent weeks. He recently visited the Falls with his parents.
"He did tell me that he believed a man could go over that Falls and survive, going to a certain area of the falls," his father Raymond said Wednesday on CBS News' The Early Show, but he didn't take his son's comment seriously.
Stunned tourists described seeing Jones float by on his back Monday in the swift Niagara River, go headfirst over the churning 180-foot Horseshoe Falls on the Canadian side, then pull himself out of the water onto the rocks below.
Jones was not seriously injured and remained hospitalized in stable condition.
Surviving a leap from Niagara Falls had intrigued Jones for years, said his parents, who spoke to him briefly after the jump.
"I said to him how foolish he was to do such a thing and he's lucky to be alive," Raymond Jones told Early Show co-anchor René Syler. "I have some admiration for him, although I was quite shocked."
Jones' friend Heather Cleveland says she thinks he was trying to commit suicide.
"He said 'this is the last day you're going to see me' and I tried to talk him out of it, but there's no talking somebody out of something like that," she said.
His father disagrees that Kirk was trying to kill himself.
"I think he believed he had a way of going over the falls without being killed," Raymond Jones said. "He chose the spot he wanted to go over with and he had a firm belief that he would come out OK."
Brian Merrett, chairman of the Niagara Parks Commission, called the stunt "stupid."
"Our people went down in the gorge and got him," Merrett said. "That's why we don't condone this. It puts all of our people — the fire department, the paramedics, everyone — at risk to do the rescues."
"I don't believe that he believed that anybody's life would be endangered by what he did," said Raymond Jones. "He's not that kind of boy."
"Charges will be laid to include nuisance under the criminal code of Canada," said Paul Fortier of the Niagara Parks Police.
Fortier said police believe they have a videotape of the jump made by someone who accompanied Jones. That person has not been charged.
Fortier said Jones was undergoing psychological tests.
Water rushes over the falls at a rate of 150,000 gallons a second.
The only other person known to survive the trip with no protection was 7-year-old Roger Woodward in 1960, reports CBS News Correspondent Jim Axelrod. The boy was wearing an inflatable ring when he was thrown into the water in a boating accident.
No one has ever survived a trip — with or without safety devices — over the narrower and rockier American falls.
Since 1901, 15 daredevils have taken the plunge in barrels or other devices, including a kayak and a personal watercraft. Ten survived, said Niagara Falls historian Paul Gromosiak.
Gromosiak theorized Jones owed his survival to a "water cone," caused by the buildup of air pressure, that cushioned his fall. "Otherwise he would have been killed," he said.
Suicides are not uncommon at Niagara Falls, although police are reluctant to give numbers.