In Sanctum, Papua New Guinea is home to the last unexplored region on the globe - an expansive underwater network of caves. Hard-nosed caver Frank McGuire (Richard Roxburgh) and his team are looking for a channel that leads to the ocean.
An unexpected storm closes the mouth of the cave. The group of cavers - which includes of Frank, his 17-year-old son Josh (Rhys Wakefield), billionaire adventurer Carl Hurley (Ioan Gruffud) and his girlfriend Victoria (Alice Parkinson) - must find a way to survive, even as food and oxygen dwindle.
Sanctum uses the ground-breaking 3D photography system developed by executive producer Cameron's team on Avatar. The underwater shots are stunningly breathtaking. The crew manages to get into some really tight spots, resulting in some spectacular close-ups of the divers in extreme conditions.
Despite lacking in depth at the start, as the film progresses, director Alister Grierson shows the darker side of the human psyche - the one that emerges when people are pushed to the edge.