“Sanctum” is an epic journey of a movie, swirling with thrilling sequences, and otherwise weak content.

The film centers on a group of rich and adventurous underground cave explorers, delving into the proverbial holy grail of caves, the colossal South Pacific Esa-ala Caves.

Once an unexpected storm rolls through the region, the caves quickly flood, forcing the team deep into the caves, its escape path cut off by boulders.

At this point, the team’s only hopes of escape lay in the slim chance of finding an unknown route leading to the ocean, as the treacherous caves pick off team members, one by one.

At its core, “Sanctum” is two different movies: a beautiful, unrelenting thriller, and a lame B-grade horror movie.

It is chock-full of ultra-cheesy dialogue, due in large part to poor acting— the kind you’d expect in a cheap SyFy channel production.

The only convincing character in “Sanctum” is Frank, hard-nosed expert diver, team leader, and the father of teenager Josh (Rhys Wakefield).

Richard Roxburgh does an admirable job playing the part, burdened with trying to save everyone during this disaster, while attempting to be a good father to his son.

Other actors’ performances are very visibly forced, and could be done without.

On the other hand, the film’s story and its environments are so awesome that they adequately compensate for those faults.

“Sanctum’s” setting is truly grand, and, correspondingly, is visually stunning.

The film’s 3-D is very well shot, and provides a wealth of visual depth, rather than ruining director Alister Grierson’s admirable work.

As a result, “Sanctum’s” action is equally as immersive, enveloping the audience in every horrifying mishap that occurs throughout our characters’ journey.

The movie actually manages to make you care about the horrible things happening to these people even though the bulk of the characters are not, in any way, interesting.

Despite “Sanctum’s” conflicting duality, its plot is engaging and enjoyable, and it’s a movie definitely worth experiencing.