Do you think it's possible that in Titanic, Jack Dawson was a well-meaning time traveler, whose sole purpose for being on the Titanic was to stop Rose from killing herself? Maybe like Dr. Sam Beckett from Quantum Leap, striving to put right what once went wrong? Driven by an unknown force to change history for the better?
If so, the Jack really needed his own Al, to appear in the form of a hologram that only Jack could see or hear. Then Al would have told him that he should maybe let Rose sink. Because if he didn't, then something a whole lot bigger would sink instead.
Let's review the facts.
Don't go overboard
Answer me this: if you were to fall overboard while on a cruise, out in the middle of the ocean, would the ship come back to get you?
These days, the answer is yes. As soon as you were discovered to be missing, someone would go back and search for you, somehow. With cruise lines having to worry about being sued for everything from undercooked filet mignon to the ship rocking too much and making someone sick, losing a passenger overboard, no matter the reason, is probably one of their worst nightmares. And to have the person that fell overboard die? That do NOT want that to happen, obviously.
What about the Titanic then? It was full of people, both rich and poor. It's safe to say, sadly enough, that if one of the folks from the lower class were to fall overboard, the captain may not have turned the ship around.
But Rose? She was one of the swanky passengers, so there's a really good chance that they would have gone back for her.
Jack to the rescue
Just as Rose is about to jump overboard and end her life, along comes Jack to save the day. It's his job, right? To go back in time and save people? Make things right?
Jack, you just killed 1,503 people
But he saved one, right? Little did he know, in the original timeline, Rose jumping overboard and going missing made the the captain stop the ship. Actually, it was her irate mother who “convinced” him to stop it. Stopping the ship meant they missed that iceberg, and everybody lived.
Jack planned his own death
In the end, after saving Rose from suicide, only to kill 1,503 people instead, Jack was overcome by grief, and sacrificed himself to save Rose. Again.
Jack is the worst time traveler ever. Not only does he not foresee the consequences of his actions, but he also forgets that he could get back to his own time, convince his future self not to go back and save Rose, and everything turns out hunky dory for everyone. Except Rose, of course. Instead, he dies, along with 1,500+ other people.
But hey, on the bright side, Jack can't go back in time and pull any more boners like that one!