Video Extras 6: Beneath the Waves

Kate, Jonathan and Kathy talking

Beneath the waves diaries

One last challenge before they can head home... how did our scientists get to grips with life underwater?

Ellen's diary
Jonathan's diary
Kathy's diary
Mike's diary

Find your own lab

Want to take an interest in science deeper - but in your own time, and perhaps without the need to be shipwrecked? Explore the Open University's many ways to study science .

Swim with the fishes

Ready for some deep sea diving, but no oxygen tanks? No problem, if you understand pumps and pressures.

Kate	Now you both looked at me in absolute horror, but is it really going to be that hard to supply me with air when I'm underwater?
Kathy	Well if you were just a little way underwater, you know 10, 20 centimetres, we could just give you a snorkel.
Kate	Yeah.
Kathy	But the problem is, the deeper you go, the bigger the water pressure. So we have to provide air at the right pressure for you to breathe.
Kate	Why is that though?
Jonathan	Well basically it's all the water above you is squashing everything.
Kate	Yeah.
Jonathan	So your whole body is at higher pressure and I think your your lungs just can't expand to breathe normally. So the only way that they can, you can breathe normally is if we supply you with air at the pressure of the water that you're at.
Kate	Wow!
Jonathan	So that means the air that we feed to you has to be compressed basically. So we have to build a pump.
Kate	So, I mean how does - just looking at this I don't think I've ever seen inside a pump. How does it actually work?
Jonathan	It's really simple, you have a tube with this piston on.
Kate	Yeah. Yeah.
Jonathan	And when you push it along the tube, it compresses the air. Which obviously forces it out.
Kate	Okay.
Jonathan	There's actually a little plastic ring here.
Kate	Yeah.
Jonathan	Which when you push it, compresses the air, and when you pull it back it lets air in. It's a really clever little thing. It's very simple but it allows you to basically compress the air.
Kate	Right, but - also allow air constantly to come in to then be compressed again?
Jonathan	That's right. I mean if you block the thing, it will just compress the air. But if you have a tube that goes down into your breathing apparatus it will push the air down there, but a higher pressure.