The Final Reckoning features a stunt so dangerous that the director had to shut down Tom Cruise's obsessive reshoots.

The result is a breathless water-churning subaquatic sequence that has Ethan Hunt caught in the undertow – shot in an 8.5 million litre water tank on a gimbal that can rotate on command. In the middle of it all,

"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.