This performance is a repetition of a very simple action. Miyajima counts down from 9 to 8, 7, 6, ... 1. When the number is "0", he inhales deeply and plunges his face into the basin of water in front of him. Hold your breath for a moment, then raise your face again and count down again. Repeat the process. The speed with which he counts and the volume of his voice is up to him. They can count as fast as they want, and as loud as they want, and as long as they put their face in the water.
When he is counting down, the number "0" is a metaphor for "life" and "0" is a metaphor for "death". The repetition of this represents the Buddhist view of life, "reincarnation" or "life and death," the dynamism of "life" that repeats itself forever. When Miyajima is countering, he is acting with thoughts of human "joy, anger and sorrow"; when he is at zero, he is thinking of death.