The Curious Case of Benjamin Button star insists he isn't scared of getting older, but often wonders how his life will finally end.
The 45-year-old actor said: "I'm more afraid of how I'll go. Fire and tight spaces don't appeal... A shark would be interesting."
The Curious Case of Benjamin Button is a big screen adaptation of F. Scott Fitzgerald's 1921 short story.
In the movie, Brad plays the title character - a man who is born with all the physical attributes of an old man, and slowly grows back into a young child.
Brad recently revealed he can't wait to grow old because he thinks it will make him more intelligent.
He said: "I like the wisdom that comes with age. I wouldn't trade it for youth any day."
The Curious Case of Benjamin Button - which also stars Cate Blanchett - received 11 nominations at this year's BAFTA Awards, with Brad named in the Best Leading Actor category.