Why a horrific sea beast kills again and again

“The Swarm” carries a strong environmental message — with a horrifying beast at its killer core.

“What I really wanted to do was make a monster movie in which our characters know something is out there, but they’re not sure what it is,” executive producer Frank Doelger (“Game of Thrones”) told The Post. “They know what it’s doing, and as the story progresses they begin to solve that mystery.”

The series, premiering Sept. 12 on The CW and adapted from Frank Schätzing’s 2004 novel of the same name, is an international co-production utilizing actors (mostly unknown here) from many different countries. The action ping-pongs back and forth from locations including Vancouver, France, Scotland and Germany, but Doelger said it was mainly shot in one locale in order to stay true to its green philosophy.

“When we got our first review in International Variety they criticized the show, which was supposed to be about he climate, for this carbon footprint we must have burned up going to all these locations,” he said.

“But because we wanted to make a green production, and because we were coming out of the pandemic, we decided the only way to make this safe and viable and responsible for a green project was to shoot it all in one location — and we found an amazing variety of locations in Italy.

“It was very gratifying when we notified Variety about that,” he said. “They published a correction.”

“The Swarm” revolves around a giant sea beast, glimpsed only briefly in each episode, that slowly starts to terrorize and kill people in open waters for reasons unknown as scientists around the world try to stop the bloodshed by figuring out the beast’s motives — and how to stop it.

“They discover the monster is actually us,” said Doelger. “That it’s something out there that we have done that has driven it to do what it’s doing. It’s very much about how we have put ourselves in a situation where the climate is turning against us.”

Doelger said he was inspired by a famous filmmaker and Emmy-winning HBO series when creating “The Swarm.”

“What we wanted to do was take a leaf from Steven Spielberg and try to reveal the monster as little as possible in the episodes,” he said. “And I was very inspired by ‘Chernobyl.’ What I really loved about that was how, through sound and music, they kept the presence of the [nuclear] reactor; you don’t see it very often, but you know it’s there.

“We used lots of shots of the ocean to keep the presence or threat as we go and wanted to make the seas a character as well — just to bring that home and keep the monster alive even though we don’t see much of it.”

Doelger said “The Swarm” is likely a close-ended series.

“One of our characters says in the final episodes, ‘If the oceans die, we die.’ So we wanted to make a story that ended on a hopeful note,” he said. “The characters believe that something can be done to remedy the situation.

“We didn’t want a story in which you walked away feeling that it’s hopeless.”