"How much money does James Cameron need?," a friend asks. "I'm guessing he can pump premium into his car even if it takes regular. So why would he put his name and then his face on commercials for Sanctum? Which, to be generous, is more or less mediocre. Is it because Cameron believes in 3D? I get that. He should champion good 3D movies. But this? Why?"
Partial answer: Because Cameron is simply queer for almost anything to do with underwater exploration and/or adventure, and because he godfathered this film and is therefore bonded and protective of it, come hell or high water.