James Cameron's planned descent to the bottom of the Mariana Trench may carry with it a nice bonus.

The 56-year-old director, who has earned over $300 million (so far) for his "Avatar" blockbuster, has commissioned Australian engineers to build a submersible capable of descending more than six miles to the deepest point in the ocean. The sub is expected to cost somewhere around $3-$4 million.

Cameron's reasons for taking the plunge have more to do with his love of deep sea exploration -- but persistent rumors say that he'll also shoot some 3-D footage for the next "Avatar" movie. In addition, whether because of good timing or planned glory, Cameron's crew will also be in the running for the $10 million X-Prize for deep ocean exploration.

The cash award is being offered in honor of the fiftieth anniversary of the Trieste -- the only manned submersible to ever reach the bottom of the 35,994-foot deep depression in the southern end of the Mariana Trench. As part of the requirements for winning, the project must be privately-funded and reach the bottom twice.

“We are using lightweight but very strong carbon composite materials and other advanced technologies very different from the Trieste, which was a hollowed-out cannonball,” Cameron earlier told The Times. “We believe we have solved most of the technological challenges to returning to the Mariana Trench. The real trick now is to make such vessels lighter, cheaper and more attractive to industry.”

To see an illustrated mock-up of Cameron's electric-powered sub, check out The Daily Mail's story here.

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