This technique I learnt from a youtube tutorial video and just thought i would share it with you...
Equipment= A CD (preferably blank), Camera with long shutter speed capability, Tripod, something to apply water droplets to the back of the disk, a Torch or portable light source, Also a cable release if possible is handy to prevent camera shake.
Method: Set the camera up facing down on the overturned disk that you carefully dripped water on, then whilst lighting is good, set your focus then switch to manual focus to avoid AF. Turn off all lights and make sure you are in a dark area (long exposure can easily lead to over exposure).
Set the camera to 'Manual' mode and stop the aperture down to the largest number (Eg: f22-29) and set your shutter speed to "BULB". Trigger your shutter then move your torch/lights source around and above the water covered disk. (Standard exposure time can be around 10-30 seconds or as desired)
Results:
Any Questions? Please ask...