This is a project I like to revisit every summer. I visited the local consignment stores and picked up a nice clear glass bowl and the brightest patterned shirt I could find. If you decide to try this project, here's a few tips:
1. Put your camera on manual focus and try to stay in one spot. (I used my tripod for this shoot) Let the patterns come to you.
2. Use a shallow depth of field. You don't want the patterns in the background detracting from the oil patterns.
3. Shoot fast! The oil will start to come together fairly quickly. Eventually, it will all come together as one sheet of oil on top of the water.