Exploring the deep: Director James Cameron's Deepsea Challenge

Crews examine the DEEPSEA CHALLENGER submersible aboard the Mermaid Sapphire off the coast of Australia. The sub is the centerpiece of DEEPSEA CHALLENGE, a joint scientific project by explorer and filmmaker James Cameron, the National Geographic Society and Rolex to conduct deep-ocean research. (Photo by Mark Thiessen/National Geographic)

The DEEPSEA CHALLENGER submersible begins its first 2.5-mile (4-km) test dive off the coast of Papua New Guinea. The sub is the centerpiece of DEEPSEA CHALLENGE, a joint scientific project by explorer and filmmaker James Cameron, the National Geographic Society and Rolex to conduct deep-ocean research. (Photo by Mark Thiessen/National Geographic)

Filmmaker and National Geographic Explorer-in-Residence James Cameron gives two thumbs-up as he emerges from the DEEPSEA CHALLENGER submersible after his successful solo dive to the Mariana Trench, the deepest part of the ocean. The dive was part of DEEPSEA CHALLENGE, a joint scientific expedition by Cameron, the National Geographic Society and Rolex to conduct deep-ocean research. (Photo by Mark Thiessen/National Geographic)

Filmmaker and National Geographic Explorer-in-Residence James Cameron emerges from the Deepsea Challenger submersible after his successful solo dive to the Mariana Trench, the deepest part of the ocean, Monday March 26, 2011. The dive was part of Deepsea Challenge, a joint scientific expedition by Cameron, the National Geographic Society and Rolex to conduct deep-ocean research. (AP Photo/Mark Theissen, National Geographic)

Crews conduct in-water testing in Papua New Guinea of DEEPSEA CHALLENGER, the submersible that explorer and filmmaker James Cameron piloted to the bottom of the Mariana Trench. The vessel is the centerpiece of DEEPSEA CHALLENGE, a joint scientific project by Cameron, the National Geographic Society and Rolex to conduct deep-ocean research. (Photo by Mark Thiessen/National Geographic)

Crews conduct in-water testing in Australia of DEEPSEA CHALLENGER, the submersible that explorer and filmmaker James Cameron piloted to the bottom of the Mariana Trench. (Photo by Mark Thiessen/National Geographic)

Explorer and filmmaker James Cameron inside the pressure sphere simulator at Acheron Project offices in Sydney, Australia. The actual sphere where Cameron sat aboard the DEEPSEA CHALLENGER during his descent to the bottom of the Mariana Trench has an interior diameter of 43 inches and provides life support, communications and control of the submersible. (Photo by Brook Rushton)

DEEPSEA CHALLENGER, the submersible designed by explorer and filmmaker James Cameron and his engineering team to travel to the bottom of the Mariana Trench, is lowered into the water for testing off the coast of Australia. (Photo by Mark Thiessen/National Geographic)

Swinging above the docks in Guamâs Apra Harbor is the Trieste, the submersible that took Don Walsh and Jacques Piccard on the first and only successful manned dive to the bottom of the Mariana Trench. 52 years later, explorer and filmmaker James Cameron made the second successful manned dive to the deepest part of the ocean. (Photo by Thomas J. Abercrombie)

After their successful nine-hour dive in January, 1960, to the bottom of the Mariana Trench, Don Walsh and Jacques Piccard emerge from the bathyscaphe Trieste. 52 years later, explorer and filmmaker James Cameron made only the second successful manned descent to this deepest part of the ocean. (Photo by Thomas J. Abercrombie)

Jacques Piccard and Don Walsh emerge from the bathyscaphe Trieste following their successful manned descent to the bottom of the Mariana Trench in January 1960. (Photo by Thomas J. Abercrombie)