So my opinion on the matter is that both relate and influence each other. I think that it can be possible to answer your question if it was worded absolutely correctly (though im not sure how you would)... The way you had it worded it was definitely opinion based
So I might get some details wrong, but if I remember right he really wanted to see the titanic wreckage at the bottom of the ocean, so he kinda wrote a movie to get hollywood to pay for it!
So all the clips you see (maybe check youtube if you are interested) are actually recent shots of the crew going down to the wreckage to look at the ship! they are not historic or computer generated images, they are real
and james cameron is a big ocean guy. he loves the ocean. he also, i think a year or so ago, took a submersible to the Marianas Trench - the first human ever to do so.