Some have theorized that Jack (Leonardo DiCaprio) is actually a time traveler sent back in time to save Rose (Kate Winslet) from committing suicide on the Titanic. If he hadn’t been there to intervene, she would have jumped. The ship would have had to stop its voyage and wouldn’t have hit the impending iceberg, thus changing the course of history forever. The evidence to back this one up is pretty solid. Jack has no money from this time period and so he has to gamble for a ticket onto the ship rather than simply purchase one, and he consistently references landmarks that just didn’t exist in 1912, like Lake Wissota, a man-made lake built in 1917. If nothing else, this theory just gives us the peace of mind that Jack possibly didn’t die at the end, but rather traveled back to his rightful period.