The experiment below was captured by the Brigham Young Unversity's Splash Lab, and here's a description of what's happening:
This stream of water is a simulated urine stream entering a body of water similar to a toilet. The amount of splash is considerable and should make one reconsider standing up to urinate. The repeated impact of the droplets opens up a large and interesting cavity with multiple ridges. Each droplet forms a small cavity wherein the next droplet can pass through and form a cavity an additional cavity creating a chain of small cavity structures. Splash is formed both from the initial impact as well as the collapse of this large cavity. The process repeats itself over and over creating a real mess.
Who knew pee could be so fascinating?