Soucek prepared for his 1984 Niagara Falls stunt by researching previous attempts, by sending unmanned barrels over the falls to test the currents, and by dropping his barrel off the Niagara Escarpment in Hamilton to test its shock absorbence. Soucek's custom-made barrel was nine feet long and five feet in diameter. It was bright red and bore the words, "Last of the Niagara Daredevils - 1984" and "It's not whether you fail or triumph, it's that you keep your word... and at least try!" On July 2, 1984, the barrel was rolled into the Niagara River 1000 feet above the cataract of Niagara Falls with Soucek inside. In seconds, the barrel was swept over the brink. Shortly after, Soucek emerged bleeding but safe.
Soucek was fined $500 for performing the stunt without a license. He had also spent $15,000 on materials and labor and $30,000 to film the stunt, but quickly earned back all his costs from sales and interviews. Having tasted success, Soucek decided to build a museum at Niagara Falls, Ontario in which to display his stunting paraphernalia. He convinced a corporation to finance a barrel drop of 180 feet from the top of the Houston Astrodome into a tank of water to pay for his project.
On January 19, 1985, as Soucek was enclosed in his barrel, 180 feet above the floor of the Astrodome, the barrel was released prematurely and began spinning as it fell toward the floor. Instead of landing in the center of the tank of water, the barrel hit the rim. Foam pads which had been placed at the bottom of the tank to cushion Soucek's fall had floated to the surface before the barrel was released. Soucek, severely injured, was still alive when he was cut from the barrel but died while the Astrodome stunt show was still going on. Stuntman Evel Knievel had tried to persuade Soucek not to go through with the stunt, calling it "the most dangerous I've ever seen".
Soucek is buried at the Drummond Hill Cemetery in Niagara Falls, Ontario, Canada.
Soucek was quoted as saying, "There is no heaven or hell; there is no God. It's all a myth. You're born, you live, one day you die and that's it."
- Berketa, Rick. "Niagara Falls Daredevils: a history". Niagara Falls Thunder Alley. Retrieved August 18, 2012.
- Warwick, Peter D. A. (Spring 1995). "OVER THE FALLS IN A BARREL". Invention & Technology Magazine. American Heritage. 10 (4). Archived from the original on July 9, 2010. Retrieved August 18, 2012.
- Bailey, George. "Karel Soucek's barrel July 2, 1984 - being towed to shore". Niagara Falls Public Library. Retrieved August 18, 2012.
- Associated Press (January 21, 1985). "35,000 Watch as Barrel Misses Water Tank : 180-Ft. Drop Ends in Stunt Man's Death". Los Angeles Times. Retrieved August 18, 2012.
- "Niagara Falls". Free Presbyterian Church. 1999. Retrieved August 18, 2012.