Pretty simple, Iain. A glass tumbler with a clear bottom - no text or anything. Some ripped up coloured tissue on the floor under the tumbler and some water in the tumbler with a couple of drops of fairy liquid in. The shot I've used was just from pouring the water in, but later I used some oil - you can see those weird-ass looking things on my Flickr.
The shot was taken with a 105mm macro lens open at 2.8 and lighting was a desk lamp - as you can see from the reflection. I also did a proof of concept shot at work using a 70-300mm Tamron on the macro setting and that worked just as well. I'll upload those when I get a chance.