Wanted to try bubble photography and although it's a hit and miss process some of the shots are pretty cool.
Setup is really easy - prop up a shallow glass dish with about 2cm of water and drop oil into it. Swish it around to get some interesting patterns. Whatever you put underneath will form the diffuse background and then illuminate from the side using a flash. Simple!

After adding more and more oil I found that rather than getting loads of separate bubble clusters they started merging getting bubbles inside bubbles.