I’m breathing in my own carbon dioxide. It builds up in the body and affects the muscles... You have to overcome all of that while you’re doing it, and be present.

"I had to train myself how to breathe. There were times I would pass out physically; I was unable to get back into the cockpit," Cruise says.

Tom Cruise’s dedication to practical stunts reaches new depths in Mission: Impossible – The Final Reckoning, with Empire magazine revealing the actor risked hypoxia while filming an intense underwater sequence.