"When I'm not doing my day job as a Hollywood movie guy, I'm doing my other job as an ocean explorer," Cameron tells PEOPLE

Move over, TitanicJames Cameron has another ocean-themed project coming your way.

Executive produced by Oscar-winning Cameron and Emmy-winning filmmaker Simcha Jacobovici, National Geographic’s upcoming investigative documentary, Atlantis Rising, sets out to unravel the mystery of the lost city of Atlantis.

The film tracks a team of archeologists, scientists and historians as they travel throughout the Mediterranean Sea in an attempt to search for the true “Atlantean” civilization — and a possible location for the mother city, the lost city itself, using cutting-edge technology and Plato’s ancient writings as a virtual treasure map to lead the way.

PEOPLE can exclusively reveal a sneak peek at the documentary, in which Jacobovici travels to the Pillars of Hercules, the ancient name given to a point that flanks the entrance to the Strait of Gibraltar, to investigate what just might be a startling discovery.

“This legendary diver in these parts, that they nicknamed The Panther, shot this video footage,” Jacobovici tells Cameron via Skype. “When I got images of it at the beginning, I thought: ‘This is a joke.’ ”

“But when I looked at still frame grabs, it looks like an underwater Nuragic [site],” he continues. “It’s big — it’s got pillars, it’s got steps, it’s got circles. It’s the Hollywood version of Atlantis, and it’s supposed to be right here, where we are.”

As for how that scene pans out? Stay tuned to find out — but one thing’s for sure, and it’s that Cameron believes exploring myths — and what we can learn from them — is important.

“That’s how the ruins of Troy were found!” Cameron tells PEOPLE. “With Plato, we have only fragments from Critias and Timaeus, but yet this fragmentary story has intrigued people for the 2,400 years since he wrote it.”

“When I’m not doing my day job as a Hollywood movie guy, I’m doing my other job as an ocean explorer,” he continues. “The payoff is that in the course of searching for Atlantis and exploring the possible sites, we came up with some pretty good evidence that there was in fact a ship-based trading culture outside the so-called Pillars of Hercules, which is the Strait of Gibraltar, just off the coast of Spain. That’s pretty big.”

In the course of the expedition, the investigators discovered six ancient anchors that could date back to the Bronze Age and that together may be the greatest ancient anchor hoard ever found on the Atlantic side of the Strait of Gibraltar.

“The anchors are something that people haven’t seen before,” says Cameron. “Is it proof that Atlantis exists? No, of course not. But it’s very intriguing, because it’s now physical evidence for a hypothesis that’s been out there for a while.”

As for Jacobovici? Well, he’s even more convinced.

“I think a lot of people when they hear the word ‘Atlantis,’ they put it in the same category as alien abduction. That is simply not the case,” he tells PEOPLE. “Somebody wrote this story down, and it’s not just anybody — it was Plato, one of the most famous philosophers in history.”

“You can’t just think of Atlantis as one spot that people argue either existed or didn’t exist,” he adds. “Reading the original text very carefully — and it’s amazing how many times you can read the same pages and not see it — Plato doesn’t say it’s just a spot. He says it’s a civilization. It’s an empire. If thousands of years from now somebody was looking for American civilization, it wouldn’t just be about finding Manhattan.”

“Once we realized that, and started visiting places like Sardinia — I mean, there are 7,000 temples on Sardinia that more or less match Plato’s description of Altantean architecture!” he continues. “I was blown away.”

And looking back, Jacobovici is as hopeful as ever about one day discovering proof of the existence of a mother city.

“I do believe, at the end of the day, that wherever you have an empire, you have a mother city,” he says. “If you have an America, you’ve got a Washington, D.C., you’ve got a New York. If you’ve got a Roman empire, you have a Rome. You don’t have a civilization without a mother city and I believe there is one here.”

“I can’t describe the feeling,” Jacobovici says of filming the documentary. “It’s easier to find a needle in a haystack than it is to find 4,000-year-old anchors in the Atlantic. When the stars all lined up, the archeology and the story combined, it was breathtaking.”

Ultimately, both men agree that at the end of the day, everyone has their own fantasy of what Atlantis was.

“There’s this sort of Disney idea of it that’s come about,” says Cameron. “I certainly don’t think it was ever that, and Plato may have just been doing sort of the Ancient Greek equivalent of science fiction. But wouldn’t it be amazing if we could find that there was actually some substance behind the myth?”

Atlantis Rising premieres Sunday at 9 p.m. ET on the National Geographic Channel.