synchronization is the word. dropping the shot glass into the bigger one, shutting the picture before the green mixes up with the clear water, and before the shot glass hits the botton.
For every failed attempt (there were quite a few) had to change the whole water.
set up is easy, 2 strobs, one everhead with the beauty dish, and the second in the back between the stand and the background, pointing the the background with a honeycomb grid upwards, minimal power for both to freeze the action. canon efs 50mm 1.8 (the real cheap one) at f7.1 with 1/250 shutter speed iso 160