Now that he seems to have filmed all there is to document in the deep sea, particularly regarding the wreckage of the Titanic, James Cameron apparently has a new obsession: indigenous tribes of the Amazon. Recently he spoke about the Achuar people, who'd seen Avatar and responded in a way that made him alter his plot ideas for the film's sequel. Now he's talking about making a 3D documentary on Brazil's Xikrin-Kayapo tribe. He has already filmed a short piece about their opposition to a major dam project in their area (the Belo Monte hydroelectric plant), which will be included as a bonus feature on the next Avatar DVD release out this Christmas. The feature will be more on the tribe's life and culture.

Cameron, who likened the plot of Avatar to the tribe's issue with the dam construction, could learn a few things from other recent documentaries about Amazon peoples. There's Joe Berlinger's Crude, which also involves tribal life disturbed by modern industry, though it's more of a legal doc than an ethnographic work. And Jose Padilha's anthropology expose Secrets of the Tribe, which details what not to do when studying and documenting indigenous groups. Such as allowing them to be experimented on or turned into personal concubines. I'm sure Cameron has higher ethics than that, but there's always the argument that merely bringing cameras into these societies is bad for them.

Now what I'd really like to see Cameron do with his 3D cameras down in Brazil is document his truthful answer to Piranha 3D, which we know he despises. How will the fish -- including some varieties of piranha -- living in the Xingu River be affected by the dam? Answer: many will likely become extinct.