Sanctum is one of those classic stories about a team of distinct personalities lending their specific skills to a highly specialized mission. Then something goes wrong and those skills either help them escape or seal their doom.

In a team of cave divers, Frank (Richard Roxburgh) is the tough as nails veteran, who’s alienated his son Josh (Rhys Wakefield) with his disciplinarian ways. Judes (Allison Cratchley) is the Sigourney Weaver look-a-like who’s daring enough to follow Frank. Carl (Ioan Gruffudd) is the fun loving rich adventurer showing his babe Victoria (Alice Parkinson) some excitement. George (Dan Wyllie) is the techie on the monitor and there are some other people. Character development is proportionate to how soon they die.

The Imax 3D looks great. The film fills the whole Imax frame, not like some of those letterboxed blow-ups. The dimensions of depth are clear so it looks like you’re really looking into a scene, not just layers of footage converted at different levels. An interesting effect is when the camera bobs half under the water, because the wet part is distorted while the dry part remains clear.

The film builds as much suspense as it can on the diving alone. Carl does a daring base jump into the water. The crew sends lights after the divers via remote control. A tank leak fills a diver’s mask and threatens to sink her. That’s all dangerous or technical, but it seems like you’d have to really be a pro diver to find any of it suspenseful.

Even when the film becomes Poseidon Adventure in a cave, it feels realistic but not necessarily dramatic. A rush of water makes it dangerous for the team to climb to an exit, and when a boulder seals them in it’s going to be even tougher to find an alternative path. You’re still watching people swim or climb and taking their word for it that it’s hard. I trust their word, but I’m not invested.The story is pretty hardcore. Frank outright euthanizes a diver who’s just not going to make it through the caves. There’s not enough wetsuits so they have to warm up Victoria. George gets the bends. I won’t spoil this one but someone gets their skin caught in climbing gear and that’s graphic. These are all really deadly conditions that emphasize the danger, but in a script they’re just benchmarks and excuses for picking off team members.

It must have been really hard for director Alister Grierson to film in those caves and get any footage that can even cut together, let alone make sense of a narrative. I would have been more impressed if John Garvin and Andrew Wight had written a real script. So they use a disaster to work through Josh’s daddy issues. So does every disaster movie. Sanctum is just so dire it’s no fun.