Deep Dive With Sanctum Director Alister Grierson

Jordan Hoffman: How much of this was shot on a sound stage and how much was shot in a cave? Especially the specific cave you mention?

Alister Grierson: Well, I don’t want to give too many spoilers away, but I can let you know there isn’t actually a cave in Papua New Guiniea. We just made that up.

Jordan Hoffman: Made up?!! The beginning of the film says it is based on a true story?

Alister Grierson: Yeah, no, that’s based on a true event that happened in Australia, where Andrew was leading an expedition of 15 people - they’re trying to break a world record, a cave diving length record, and the last day of the expedition the cave system collapsed and they’re all trapped for two days. Eventually they all got out and survived, but the terror of that experience stayed with him.

Jordan Hoffman: That’s what informs the screen play?

Alister Grierson: Yeah very much so.

Jordan Hoffman: Did they come to the same realization that they had to explore to escape, to follow the water, because they could not exit the way they came in?

Alister Grierson: Exactly, they had to explore a new way out of the cave, and eventually they got out. In terms of doing a fictional dramatic story, we need to come up with a whole bunch of other series events to create conflict and chaos. So we cherry-picked a whole bunch of other events that either Andrew had witnessed or heard from cave-diving buddies, and then we strung them to together to create something as action-packed as we could. But the cave itself is shot obviously in some on a stage, some in a real cave, but all in Australia. We set the film in Papua New Guinea because it felt like to me that the mention of the jungle and the tribal elements, had an interesting metaphorical effect for me. You’re just going further and further back in time, you know. So I start the movie at a small port and then we end up at a custom village, and then we’re in a cave, and then we’re going really primeval, you know? Really ancient, we’re actually in a space that’s older than humans. It was a visual motif that appealed to me.