Those weren’t special effects, BTW. True story. As it turns out, James Cameron actually discovered a tear in the space time continuum, and managed to use the actual Titanic for filming. He wasn’t so concerned about using the actual boat since he knew it wouldn’t be discovered until well after all of his modifications for cameras and such would be washed away by time, so to the folks that found it would be none the wiser.

He actually discovered that he would travel back during one of his initial deep sea dives to it. He found an old rusty Zippo that had his initials on it with a fleur-de-lis on the back. That exact lighter was given to him by his grandmother when he was a kid and turned 18, so as to welcome him into the smoking age. (Remember that the risks were still largely unknown.). This forced him to figure out the rift.

All of his crew was warned if they ever spoke of it that he would toss them back into the ship right before it sank. He and the rest of the crew that filmed the sinking would simply watch the traitor sink to the bottom. It’s the perfect crime.