"There's just me and the universe here ... there's an out of body feeling to it."

All six-feet two-inches of Cameron clambered into a replica of the pilot capsule of a deep sea submersible he helped design and build and that took him to the ocean floor, as he gave a tour of the exhibition on Monday.

It's a space only a metre-or-so wide and missing the electrical equipment that left him with "barely room for an energy bar" and descending alone inside was an experience he describes as completely isolating.

"To me it was a zen kind of spiritual experience, to be that remote from humanity," he says.

"I got to observe, to bear witness to something that no one else has ever seen."

It's pitch black that far beneath the surface, and Cameron likens his underwater explorations to being dropped in the Nullarbor Plains with just a flashlight.

In his time exploring the ocean he says there have been some close calls. In fact, he almost didn't survive seeing Titantic for the first time.

"What really happened was that the Russians hadn't dived to Titanic in a few years and when we went there they were a little rusty and the guy piloting the sub nearly ran into the ship," he said.

"We were going up this clay embankment and I had this strong feeling that the only place there's a clay embankment in the whole wreck site that I knew of ... is the clay bank caused by the bow smashing into the bottom.

"Out of a cloud of silt from the thrusters slowing down this wall of rivets came at us."

It wasn't until he surfaced that Cameron says begun to feel the sheer tragedy of the wreck - realising he had just seen the exact spot where the band had played as the ship went down.

Cameron describes himself as more explorer than Hollywood heavyweight, but admits that being a good storyteller is an essential part of discovering the ocean.

"I don't go down there to find cool aliens to put into Avatar, I make Avatar to get money to recharge the treasury to build new vehicles to go on explorations," he says.

But it is that storytelling, and ability to bring back images from the deep, that he hopes will inspire the next generation and on Monday he got the ball rolling with students from Sydney Secondary College, teaching them to drive remotely operated underwater vehicles in Darling Harbour.

It's their generation, he explains, who have the potential to make important discoveries about the ocean floor - a surface humans know less about than they do of Mars.

"There will be wonders there greater than anything we will find on Mars," he says.

AAP