When Philippe Cousteau and his wife Ashlan Gorse set off to explore The Marshall Islands, they had no idea what they would find.
An area once used for nuclear testing during the Cold War, Gorse tells PEOPLE: “We actually detonated over 60 nuclear bombs around these islands, and we completely destroyed the ecosystem, pretty much any living creature in the area.”
Having heard that sharks had returned and were flourishing in the area despite the devastation, the couple set off to investigate for their Discovery Channel Nuclear Sharks show.
“It was just a wonderful thing for the two of us because it was our first real expedition, we were leading it together,” says Cousteau.
“When we went into the water, we’d have 70 or 80 sharks swirling around us at any one time,” he says. “It was just an absolutely spectacular expedition that confirmed the fact that the sharks had somehow repopulated the island.”
But the couple also discovered a dark side during their investigation.
“Illegally half of the sharks that we tagged were caught by long-lining vessels, most likely for shark fin soup,” says Philippe. “That was a real big eye-opening, shocking experience.”
Cousteau discussed how the island’s small size and limited resources make it hard to protect their environment.
“They are doing everything they can but they’re a small country,” says Cousteau. “They need help, they need resources to protect this vast area.”
While the couple’s expedition was all about shark discovery they also learned a few things about each other.
“You should have seen the look on Ashlan’s face when we got there,” Cousteau joked. “We had a curtain for a door, a small set of bunk beds and one toilet for 17 people.”
But Gorse wasn’t fazed: “I have girl power. It was the most epic adventure I’ve ever been on in my life.”
Nuclear Sharks airs Thursday at 9 p.m. ET as part of Discovery Channel’s Shark Week, running nightly through Sunday.