Titanic is the story of a disaster. The audience knows the disaster is inevitable. How can you make a romance plot have believable stakes when everyone in the room knows everyone on screen is as doomed? Turns out all you need is a director with an obsessive interest in one of the most researched and examined historical mysteries of the last century, a fascination with pushing the boundaries of filmmaking technology, a reputation as the scariest man in Hollywood, six to ten of the most talented working actors of the time, and $200 million. And even then, you’ve got to dodge some icebergs.

James Cameron, long obsessed with shipwrecks and underwater exploration, pitched Titanic to Fox by saying that the publicity they’d get for filming at the actual wreck (which had been lost for decades) would make marketing the movie almost free. They gave him a green light without, it would seem, asking themselves what it would take to actually accomplish that filming. Which was: a miracle. The crew shot there twelve times in 1995, 13,000 feet below the surface of the ocean, in a vessel that, if it had the smallest flaw or impact on its superstructure, would have killed them all in an eyeblink. That’s all before Cameron wrote the script. And in the end, he didn’t even get the footage he wanted. So he built a full-scale model of the ship and then sunk it in a seventeen-million gallon water tank. Titanic shouldn’t exist; it should be impossible to pull something like this off. But instead of a disaster we got a miracle as big as the historical Titanic’s voyage is tragic, and an epic love story that has transfixed generations for more than 25 years.