@Space Kaijuu: Titanic, like all of Cameron's movies since The Abyss (except Avatar, which was of course shot digitally) was shot full frame on 35mm film using Super35 aperture, with the exception of the submersible scenes, which were shot using Techniscope, so as to be able to shoot more material without the ability to change reels in the camera mounted outside the submersible. (Techniscope is a 2-perf format that shoots 2.33:1 with a normal lens, so it uses half the amount of film than anamorphic does.)
Shooting on 70mm (resp. 65mm) film is not only very expensive but also very difficult because of the huge heavy equipment needed for it, so film makers do it very rarely.
@SilverWook: The VHS release of Titanic was partially open matte, showing more at the top and the bottom but considerably less on the sides. I assume the LD was the same. They often crop significantly more of the bottom than of the top when cropping to 2.39:1 from Super 35, so a full open matte 4:3 would make the vertical framing all wrong but it does allow for a 16:9 open matte like they did with the 3D Titanic.
But both of the DVD releases of Titanic and the 2D BD were OAR, so I really wouldn't expect the Abyss BD to be open matte.