A jet of water flowing into a pool creates a myriad of small whirlpools that interact with each other in complex ways. Vortices that spin in the same direction attract each other and sometimes join to form larger whirlpools. Vortices spinning in opposite directions repel and sometimes destroy each other. The lighting of the exhibit will allow people to see the rotating regions of water because the vortices create a surface depression that acts like a lens to spread the light and produce a dark spot on the bottom of the tank.