Water isn't supposed to float on top of water because well, water is water. So how are these droplets of water suspended on the surface of the water? Sound. The water is actually on top of a speaker and the acoustic vibrations allows the water drops to stay as drops on top of water.
It's a fun little experiment and NightHawkInLight explains how to do it in the video below. There is a slight trick to tweak the surface tension but hey, you never have to tell anybody.