For your curiosity, this is a one shot deal. My water tray is 42 cm. long and I drop in the middle of it and have my camera at a low angle to catch the reflection.
Behind the water tray I have a piece of tinfoil which I have crumpled up and flattened. There are several small pieces of colored gels on the flashes. The light from the flash guns bounces off the points on the tinfoil to give the bokeh effect.
This background style is unique to me and will be found only in my water drop photography.
The shutter speed at 1/2 second is necessary to allow for the process of two drops to fall and the flashes to be activated at a specific stage in the drop. It is the flash itself that freezes the action. The speed of a flash for these is at minimum, 1/20,000th of a second. Much less than this and there will be motion blur.