Make it Sink and Float it Out!

The other day I placed my cup into another cup in the sink and did what my parents always tell me, filled my cup with water all the way to the top. While I was doing this I realized that the cup I had placed in the original sink cup was floating a little because the original cup had a little water on the bottom. However, when I began to turn on the water my cup began to fill up with water and started to touch down on the bottom of the other cup. Then, when it was finally full the cup sat in the other cup perfectly full flush to the bottom of the other cup.
I was pretty amazed with this physics action. The pressure of the water caused the cup I put down to be able to sit in the previous cup. The frequency at which the water was coming down determined how fast the cup went down to the bottom. At first the cup I put down was able to bob up and down because it had no weight and the previous cup's water allowed my cup to float. Then the weight of the water, combined with pressure, and the frequency enabled the cup to fit right into the previous cup. This is decently odd but I believe that it applies to physics and it quiet fascinating.