The 42-year-old even trained himself before shooting for the final time, but says it did not prove to be helpful.u00a0"I didn't want to do that at all. So I wouldn't be constantly aware of how scared I am of drowning I had to go to a pool with this great stunt guy and dive master a couple of times a week for a month or so to train me to relax underwater without an oxygen mask," Playboy magazine quoted Damon as saying.

"That night I woke up probably four times gasping for breath, thinking I was drowning. It was terrible," he added.