This is awesome and mesmerizing. When water drops on a surface, it generally collides and bounces before merging. When that surface is vibrating, it can bounce and bounce and bounce and bounce and bounce.
When a water droplet hits a surface of water, it doesn't just merge immediately. The two liquids are each held in by surface tension. They are two separate objects. The water hits, beads, and then merges with the liquid some time after impact. But what if the impact never stops, because the surface is constantly vibrating?
Researchers at the National Autonomous University of Mexico filmed exactly this. The vibrated a dish of tap water on a speaker, and put drops of soapy water on top. (The added soap was to allow the drops to be small enough for the experiment to work. There is a size limit. Obviously an entire swimming pool can't be kept bobbing on the ocean if the water is rough enough.) The beads of soapy water just keep bouncing on top of the other water. As the researches add more beads, you can see them run along in lines, or bounce together in groups. It's an amazing video!