David Worley, Northamptonshire via Twitter asked:
Can divers use GPS whilst underwater to navigate through the water?
We put this to Professor Todd Humphreys:
Todd - Divers can't use GPS. It’s because the high radio frequencies used for GPS just bounce off the surface of water. And so, divers will have to resort to other means - sonar or other techniques - for navigating beneath the water surface.
Ben - Helen, you're a regular diver. How do you find out where you are?
Helen - Well, we have used GPS when I've been doing things like underwater surveys. What you can do is tie the GPS to a buoy on the surface and drag it along behind you. Then you can download basically where you've been. You can track your path and match that up with what you were looking at when you were underwater.