Niagara Falls: A man survived a plunge of at least 180 feet (55 meters) over Niagara Falls in an apparent suicide attempt on Monday - only the third person known to have lived after going over the falls without a safety device.

Niagara Parks Police said witnesses reported seeing the man climb over a railing up to 30 feet (9 meters) out over the Horseshoe Falls at 10:20 a.m. local time and "deliberately jump" into the Niagara River. Seriously injured, he surfaced in the lower Niagara River basin near the Journey Behind the Falls observation platform and managed to make it to shore on his own.

"He waded ashore," said Platoon Chief Dan Orescanin of the Niagara Falls, Ontario, Fire Department. "He must have gotten swept into an eddy, floated over there and was able to get out on his own.

"That's another stroke of luck," said Mr Orescanin. "If he was in the main current, he would have been swept down river."

Mr Orescanin said the man was conscious and talking at first but got quiet. He appeared to have chest injuries, including broken ribs and a collapsed lung, Orescanin said.

The man was airlifted to Hamilton General Hospital with what police initially said were life-threatening injuries. Hospital spokeswoman Agnes Bongers said later that the man was critically injured but was expected to survive.

Authorities did not release the man's name.

Horseshoe Falls, on the Canadian side of the river, is the tallest of the three main falls, higher than the American Falls and Bridal Veil Falls.

The man, believed to be in his 30s or 40s, was rescued about two hours later after fire department rescuers rappelled down the steep and rocky gorge and pulled him in a basket back up the cliff.

"It was very difficult. Between the shale and the boulders, and everything is wet and slick. It's slimy," Mr Orescanin said.

About seven rescuers struggled to carry the basket up to a point where it could be lifted with ropes suspended from an aerial truck.

"We had to basically hand-carry him back up, a foot at a time, up the rope," Orescanin said.

The rescue came weeks before daredevil Nik Wallenda plans to walk over Niagara Falls on a tightrope after convincing United States and Canadian officials to grant an exception to laws prohibiting stunting.

Although several daredevils have survived trips over the falls in barrels or other contraptions, beginning with Annie Edison Taylor in 1901, few have survived unprotected. In 1960, 7-year-old Roger Woodward was swept over the falls wearing a life jacket and survived.

Authorities don't believe Monday's plunge, on a warm and sunny Victoria Day holiday in Canada, was a stunt.

"Based on witness statements and surveillance video, it doesn't appear in any way, shape, or form that this was anything other than a suicide attempt," Niagara Parks Police Sgt. Chris Gallagher told WIVB in Buffalo.

More than 6 million cubic feet (0.17 million cubic meters) of water go over the brink of the falls every minute during peak daytime tourist hours, according to the Niagara Parks Commission.

The last person to go over the Falls unaided and survive was a 30-year-old Canadian man in March 2009. In October 2003, Kirk Jones, an out-of-work auto parts salesman from Michigan survived his plunge over the falls.

After getting the call on Monday, rescuers didn't immediately know whether the man at the bottom of the gorge had gone over the brink or entered the water at the base.

"When we heard that he had gone over the falls we were shocked," Mr  Orescanin said.