This lava field here is just full of these sorts of caves, and, actually, what this is is actually an old lava tunnel. And this is where, originally, flowing molten, red-hot lava would have been racing through this. And what happens when that's gone -- it leaves behind these sorts of tubes. But here, off the glacier, fresh water is scarce. And, you know, all of this lava field -- the exact translation into Icelandic is literally ‘no water’. But my best chance is to get in there and see if I can find some seeps coming through, through the walls of fresh water. First of all, before I even think about getting in there, I've got to make some sort of torch. Yeah, it's pitch black. 

 

I can make a torch out of some twigs and the fat I saved from the dead sheep. Get down here, out of the wind. Cave water is filtered through the rock, so it will be a lot purer than the outlying snow, which can be full of bacteria. Okay, now, what I need is just a bit of the material from my T-shirt. I've got some of this sheep's fat, wrap this round, like so. Take this bit of T-shirt and then tie that round it. Now, if I can just get a little fire going, that fat will burn really bright. Try and get this going. Okay. It’s going. I need to be really careful, because all of this is fragile, and sharp. So I'm gonna need my gloves in here. Iceland has, on average, 33 earthquakes a day, and any one of those could collapse this tube. You've got to be quick. What I'm looking for is just a good source of dripping water.