With a marketing campaign resting heavily on James Cameron’s insignia, “Sanctum” has a lot to live up to. The name-dropping is misleading, however, as Cameron is executive producer and Alister Grierson directs the film. From the early sweeping shots of a helicopter flying over the rain forests of Papua, New Guinea en route to the deepest cave on Earth, “Sanctum” resonates with the familiar epic cadence Cameron’s narratives are apt at tapping into.

In Grierson’s sophomore film, preceded by 2006’s “Kokoda,” he finds the subject for this 3D thriller in a fictional underwater cave system, shot on location in Queensland, Australia. Defined by Webster’s as both a sacred place and a place where one is free from intrusion, “Sanctum” is ripe with religious imagery and allegory. From the religious fanaticism these divers steadfastly hold in cave diving to the naming of the crew’s initial underwater discovery as St. Jude’s Cathedral, their thirst for exploration comes to supersede their instincts for survival.

Josh (Rhys Wakefield), more a climber at heart than a diver, follows his father Frank (Richard Roxburgh) on his many cave explorations around the world, despite their strained and hostile relationship. Frank’s hard-nosed, unyielding personality stands at odds with Josh’s emotional and strong-willed persistence. Nevertheless, they come to rely on each other as they trek through the interminable cavern, cyclone rains pouring in.  Father and son come to recognize their similarities, and the instincts Josh has inherited.

The diver’s live by what seems like a heartless code. In this sacred cavern two kilometers beneath the surface of the Earth, nothing is as it seems, all dignity is lost. No one is more taken aback by this than Josh, but as the push to find an escape grinds on, the others grow weary as well. Everything changes in the cave and in this adventure. If there’s one mask and two people, one person lives and one person dies. Two members won’t be lost, with acts of heroism becoming acts of recklessness and negligence, putting everyone’s lives  at risk. From Baptismal drownings of wounded divers to the choices of one life over another, the audience is converted to the coldhearted mindset the cave teaches.

The cave can be acknowledged as another member of the cast in this movie, with its ominous lessons, forbearing sounds and sanctimonious lurching, the cast refers to it as if it were alive. “She goes,” the characters say throughout the film, which is to say that a certain tunnel is worth exploring, a throughway and not a dead end.

The cave “feels” and the cave “understands,” Frank pronounces to the weary and the weak of heart. Frank’s determination and drive, once admirable to his colleagues becomes his pitfall as his actions and motives continually put their lives on the line in the name of exploration. “Down here I can make sense of this. It’s like my church. I can hold a mirror up and see who I am,” Frank explains to his son.

Cameron himself has become somewhat of an underwater aficionado in recent years, directing the documentaries “Expedition: Bismark” and “Ghosts of the Abyss 3D” in 2002 and 2003, respectively. “Sanctum” reflects this, with the National Geographic feel of the film akin to “Avatar” or even “Jurassic Park.” In an interview with Australia’s “Sunday Times,” Cameron stated his intention to film scenes for the “Avatar” sequel at the bottom of the Mariana Trench, the deepest part of the world’s oceans. “Sanctum” in large part feels like somewhat of a trial run for that lofty endeavor. Cameron also explains that “Avatar 2” will largely focus on the oceans of Pandora.

If the fear of drowning makes you squeamish, you’re better off avoiding this one, as this fear understandably looms overhead throughout the movie. The gore for the most part is kept at bay, with one minor scalping and a couple mutilated bodies. The score, from Australia’s David Hirshelder will do well to keep you in it, rounding out the orchestral pieces with eerie and original world music.

Brian Canova can be reached at [email protected].