Technically, he froze to death.
Only if they both had the knowledge and frame of mind to engi her flotation devices from the life vest rose was wearing. Otherwise the door would have sunk enough for them to freeze to death before rescue came. Provides they knew rescue was coming after a certain time.
Considering one was a socialite, and the other a freelance artist, and both had just almost been killed multiple times… no, I don’t think they would have had the foresight to come up with the exact scenario that would have saved them both.
Cameron tested this. There was room for both on the door, but only in a very specific orientation could they both stay dry. And because she was wearing more clothes than he was, even if Jack makes it out of the water, he’s still hypothermic and won’t survive.
Edit: It’s a NatGeo doc called “Titanic: 25 years later.” They’re in a pool that’s 56 degrees F. You can find it on streaming someplace, but here’s a clip. https://www.youtube.com/watch?v=YEJph0aIP-U
