But a scant few weeks later, the filmmaker and explorer is eager for himself and project scientists to dive again into Challenger Deep, an undersea valley in the trench that's the deepest known point on Earth.
"You can't over-interpret from one single glimpse," Cameron told National Geographic News yesterday afternoon, local time, from aboard the research vessel Mermaid Sapphire, in Guam's Apra Harbor.
"What I wasn't able to do is get very far up the north slope. I was looking for a fault scarp, and I wasn't able to find one before I ran out of bottom time. So we really need to go back and explore the size of the trench more."
For now, however, Cameron and his team are wrapping up what they're calling Phase One of the DEEPSEA CHALLENGE project, a partnership with the National Geographic Society and Rolex. (The Society owns National Geographic News.)
"We always planned it in two gos," Cameron said. "The first [phase] primarily focused on proving and refining the technology, [with] the second one being more science-focused once we had a proven platform."
For instance, on April 1 Ron Allum, co-designer of the project's custom DEEPSEA CHALLENGER sub, completed a dive to 3,280 feet (1,000 meters) off the coast of the tiny Pacific atoll of Ulithi. During that dive, Allum recorded images and video of deep-sea life and collected rock samples using the sub's mechanical arm. (See pictures of Cameron's sub.)
"The interesting thing about [that sample] is that it's a piece of one of the coral-growth features on the flank of a seamount," explained expedition member Patricia Fryer, a marine geologist at the Hawai'i Institute of Geophysics & Planetology.
"So we should be able to date the coral ... and that will help us figure out how rapidly that atoll has subsided."
Trench Dive a "Religious Experience"
Cameron, who is also a National Geographic Society explorer-in-residence, says the team initially planned to conduct about a dozen deep dives into the Mariana Trench during the first phase of the project.
However, an accident in February that killed two crew members and a combination of technical glitches and uncooperative weather severely whittled down the dive window.
Finally, during the record-breaking March 25 dive, Cameron's expected six-hour bottom time was cut short after a hydraulic fluid leak that disabled the sub's mechanical arm, preventing him from collecting samples, and problems with the thrusters limited the sub's mobility.
Several days later, Cameron seemed to take the technical glitches in stride: "The thing that I know from my experience of diving ... is that unless you're running a tourist sub that does the same dive everyday, day in day out, you're going to have technical problems."
Recalling his brief stint at Challenger Deep, where only two other humans have ever visited, Cameron said his first view of the bottom was akin to a religious experience.
"When you see that faint glow in your spotlights, you know they're bouncing back off the bottom of the ocean," Cameron said. "There's a while there when you think there's not even a bottom down there. You just keep going and going."
Cameron added that he hasn't suffered any physical or mental problems from the dive, but he recalls being very tired immediately following his return to the surface.
"I was just completely mentally and emotionally and physically exhausted," he said. "We had been up for two days straight ... so by the following afternoon I was completely wiped out and the second I got anywhere near a place to lie down, I just went unconscious."
If his schedule permits, Cameron said he would like to do more dives himself in DEEPSEA CHALLENGER. "I'd love to continue with the dives, but I'm not sure that if I'm making Avatar 2 and 3 over the next few years I'm going to have much time," he said.
Now that the sub has proven itself as a viable science platform, Cameron said he has no objections to other scientists going down in his stead: "I don't have to be the one piloting the sub. Other people can make the dives."
Expedition geologist Fryer said that she for one would leap at the opportunity. "I'd be the first person to take a ticket," she said. "Train me up, and set me down."
Finding Funds for Phase Two
But when future dives might occur will depend in part on how much funding support the project will be able to attract, Cameron said.
"We've got the equipment. What we need is funding to support the science not only to do the initial research but to support the analyses once the samples are taken," he said.
"And we need funding to basically just get ship charter time, which is the expensive thing. You run about a million dollars a month just in straight ship costs ... It's possible we could be back out here next year, but that remains to be seen."
Andy Bowen, project manager and principal developer of the Nereus, a remotely-operated vehicle that explored Challenger Deep in 2009, said funding for the DEEPSEA CHALLENGE project will depend on the quality of the proposals that the team's scientists submit.
"The key is, are the scientists who would use the submersible going to produce high-quality proposals that ask very good questions for which the submersible is uniquely suited to solve?" said Bowen, who is from the Woods Hole Oceanographic Institution and is not an expedition member.
DEEPSEA CHALLENGE chief scientist Doug Bartlett said he could imagine the project running into some resistance within the science community, "especially those parts of the academic environment that look over the operations of things like research submersibles for basic research," said Bartlett, a marine biologist at the Scripps Institution of Oceanography in San Diego, California.
"They tend to be pretty conservative, and Jim's sub is anything but conservative in design."
For their part, Bartlett's team is making the most of their last few days in the region to conduct more experiments. "It's such a great opportunity that Jim has provided us," Bartlett said. "We just want to maximize the opportunity to go deep and to collect material that will be of lasting scientific value."
For instance, the scientists recently sent an unmanned, baited lander into an unexplored section of Challenger Deep and successfully retrieved dozens of the small, shrimplike amphipods that Cameron saw during his dive but was unable to capture.
"We also got some beautiful [video] and still images and 3-D video from the drop," Bartlett said. "It was really very, very successful."
"I'm sure that scientists would be anxious to gain access to this [kind of] material," project manager Bowen said.
"The bottom line is that there's so little material or measurements or observations about the hadal environment"—the ocean's deepest level, below 20,000 feet (6,000 meters)—"that any information is highly sought after and very valuable. I would expect any scientist worth their salt would die for that kind of data."
Respecting the Marine Frontier
Cameron said there's no shortage of candidate sites for future dives. "If you add up the aggregate area of the hadal depths, it totals about the same as the continental United States," he said.
"So there's an entire continent's worth of ocean that's never been viewed or explored, and it's still waiting and it requires machines like the DEEPSEA CHALLENGER to do it."
While Cameron's sub is currently the only operational manned submersible that has proven capable of diving to Challenger Deep depths, it may not be alone for long. Other companies, such as Richard Branson's Virgin Oceanic and the luxury submersible-maker Triton, say they have vehicles that can make the dive and that might one day open up the experience to tourists.
But Cameron said he doubts a business could be made of such endeavors, and he worries that people will not fully understand the risks involved. With the DEEPSEA CHALLENGER, he's not interested in taking others down for pleasure.
"You have to draw a strong line in the sand between exploration and tourism. The second it becomes tourism, it's not a frontier anymore," he said.
"To me, when it's a frontier, when it's unexplored [and] when it's approached with the proper respect and the proper philosophy of curating the science and doing the imaging and sharing it with the world at large, it's justified."
Additional major support for the DEEPSEA CHALLENGE expedition was provided by the Alfred P. Sloan Foundation.