James Cameron thinks it's ''silly'' people still question why he killed off Jack Dawson in 'Titanic'.

The 63-year-old filmmaker insists he made an ''artistic choice'' to have Leonardo Dicaprio's character perish in the icy waters while Kate Winslet's Rose DeWitt Bukater stayed safe on a floating wooden door at the end of the movie, so can't understand why there are still fans insisting they both could have survived.

However, the director finds the outrage flattering because it shows how well-loved the character was.

He told America's Vanity Fair magazine: ''The answer is very simple because it says on page 147 [of the script] that Jack dies. Very simple.

''Obviously it was an artistic choice, the thing was just big enough to hold her, and not big enough to hold him ... I think it's all kind of silly, really, that we're having this discussion 20 years later.

''But it does show that the film was effective in making Jack so endearing to the audience that it hurts them to see him die. Had he lived, the ending of the film would have been meaningless ...

''The film is about death and separation; he had to die. So whether it was that, or whether a smoke stack fell on him, he was going down. It's called art, things happen for artistic reasons, not for physics reasons.''

And the director admitted he is such a ''stickler for physics'' that he spent days in the water ensuring the door was ''exactly'' buoyant enough to support a person's weight for a long period of time without them getting immersed in the water at all.

He added: ''I was in the water with the piece of wood putting people on it for about two days getting it exactly buoyant enough so that it would support one person with full free-board, meaning that she wasn't immersed at all in the 28 degree water so that she could survive the three hours it took until the rescue ship got there.

''[Jack] didn't know that she was gonna get picked up by a lifeboat an hour later; he was dead anyway. And we very, very finely tuned it to be exactly what you see in the movie because I believed at the time, and still do, that that's what it would have taken for one person to survive.''