The brutal scenes in the 1972 classic thriller Deliverance were enough to scare viewers away from canoeing entirely — but they were actually far more realistic than you might expect as actors revealed they nearly lost their lives while filming during several terrifying incidents.

The film, which had such an impact on fans it's been preserved in the US Library of Congress for being “culturally, historically or aesthetically significant”, sees four city-slicker friends from Atlanta embark on a canoeing trip in the Georgian wilderness. But things soon take a turn when run-ins with hostile local hillbillies in the backwoods lead to some horrific events — including a disturbing rape scene where one of the men is infamously asked to "squeal like a pig" by his assaulter.

The men's dangerous journey continues when they come to a treacherous stretch of rapids and this is where things took a turn for the actors in real life too. Recalling how they filmed the dramatic scenes, director John Boorman revealed how his impatience during filming in the "ferocious" Chattooga river led to a mishap the cast only "just about survived".

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He told The Guardian: "I did the scene where their canoe breaks apart on another river, which was dammed. I got them to close all the sluice gates upstream, so only a trickle came down.

"That let us build rails on the riverbed, so we could mount the canoe on them, and trigger the breakup later. When we came to shoot, I was down at the bottom of the cataract on the phone to the dam. But I got impatient and got them to open all the gates. We just about survived the avalanche of water."

The nearly deadly mishaps continued when Burt Reynolds, who played Lewis Medlock, filmed a scene that saw his character going over a waterfall in his canoe. John originally wanted to send a dummy down the rapids instead of Burt but the actor insisted he did it himself — a decision that saw him break his tailbone and nearly drown.

Recalling the incident during an interview with the Hollywood Reporter, Burt said: "They let the water go and I heard this sound—I dream sometimes of the water coming—I looked around and there was a tidal wave coming at me. I went over the falls and the first thing that happened, I hit a rock and cracked my tailbone, and to this day it hurts. Then I went down to the water below and it was a whirlpool.

"I couldn’t get out and the guy there said if you get caught, just go to the bottom. You can get out but you can't swim against it. So I went down to the bottom. What he didn’t tell me was it was going to shoot me up like a torpedo. So I went out."

Eventually, Burt emerged from the water — entirely naked after the whirlpool had ripped his clothes off. He added: "They said later that they saw this 30-year-old guy in costume go over the waterfall and then about fifteen minutes later they saw this nude man come out. It had torn everything—my boots and everything off."

Burt wasn't the only actor on set to suffer a nearly fatal accident. Jon Voight, who played Ed Gentry, also insisted on carrying out his own stunts and recalled how he was almost killed while filming a closeup shot climbing a cliff. He told The Guardian: "I almost got killed climbing the cliff; I decided I needed to do it so it could be shot in closeup, which wouldn’t be possible with a stuntman. I was about 10 feet up on the face, which was slippery and almost perpendicular.

"I told the two grips below me: 'If I start to fall off, I’m going to push off the rocks. And you’ll catch me.' I started to slip, called out and one of them caught me. There was a sharp rock inches from my head."

In the end it appeared the men's cost-cutting stunts paid off as the film, which also starred Ned Beatty and Ronny Cox, was a huge success in the box office — raking in $46 million on a $2million budget.