An expedition to explore a series of underwater caves in Papua New Guinea goes badly wrong, when the unexpectedly-sudden arrival of a cyclone blocks the only known exit. The half-dozen or so explorers trapped below ground, have to go further into the undiscovered system, in the hopes of finding another way out: can they manage it before their dwindling resources of air, power and strength run out? That, in a nutshell is the story here. Though there are also the unresolved father-son issues between Frank (Roxburgh) and Josh (Wakefield), with the latter hating the former for being far more interested in cave-diving than his parental duties. Expedition financier Carl (Gruffudd), is also trying to push the team harder than perhaps he should, to make a key breakthrough before they have to shut things down. Frankly, however, they'd have been better off not bothering with all that stuff, because it's largely unconvincing and unnecessary soap-opera, that drags down the first half of the film badly. Stick to what it does well: capturing the claustrophobic atmosphere, and the basic struggle for survival.
Indeed, it may be too good at that - as we left, I asked Chris, "So, why do people go into these caves to begin with?" The best we could come up with, was that it was just a spirit of adventure: as one character says, you can see things no-one has ever seen before. But the flaw is, there isn't much here that's worth seeing, in part thanks to the limited lighting [really, I was glad we didn't shell out the big bucks to see this in 3D, and didn't miss it at all]. I was expecting a stunning spectacle, gorgeous spires and underground structures, but there's nothing here to justify the effort, or explain the motivation. If you can ignore that, the actual escape attempt has a fair degree of tension, and as things develop, a real air of danger grows, with a sense that anyone can die at any time. By that time, however, you're more than an hour in, and overall, the main thing you'll take away is to cross "cave diving" off your list of acceptable pastimes.