MISSION: IMPOSSIBLE - THE FINAL RECKONING Brutal Underwater Stunt Pushed Tom Cruise to the Limit

Tom Cruise suffers for the stunts that he performs in his films, and in Mission: Impossible – The Final Reckoning, one of his most grueling challenges wasn’t a death-defying leap or high-speed chase, it was a claustrophobic, submerged infiltration scene that left the star nearly blind, gasping for air, and weighed down by an absurdly heavy diving suit.

Cruise recently appeared on The Tonight Show, where he pulled back the curtain on a major underwater sequence in the film. In the scene, Ethan Hunt dives into a submerged submarine, and while it looks sleek and intense on screen, shooting it was anything but smooth.

According to Cruise, he could barely see during the shoot due to intense underwater lighting bouncing off the suit’s helmet. Cruise explained:

“A lot of times I cannot see because of the reflection of the light. So, I would go in, kind of blind, spend a lot of time on the set figuring out [the movement] as we’re figuring out the shots.

“Then, when I’m doing it, I have a hard time. Plus the suit, when it’s wet, increases in weight by about 125 pounds. So, the kind of workouts and things that I have to do just to prepare for these things, it’s years of development. And yeah, and I’m producing it, so it’s also that kind of thing.”

The kind of physical conditioning needed to even move in that situation, let alone act and hit marks, is ridiculous. But Cruise being Cruise, he didn't stop there. He also revealed that because of the limitations of the breathing apparatus, he was essentially suffocating himself slowly during the shoot.

“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.”

Years of development, intense training, and still zero visibility and compromised breathing. It’s the kind of commitment that’s become synonymous with Mission: Impossible, and with Cruise. Whether or not The Final Reckoning is Ethan Hunt’s last mission, it’s clear Cruise made sure to push every physical and cinematic boundary he could… again.

This kind of dedication is the reason these films feel as tense and real as they do, and judging by Cruise’s stories, the behind-the-scenes experience is often just as intense as what ends up on screen.

Watch the entire conversation below.