How to make the Dock do the "wave"?

Recently switched from a PC to the Mac and all I can say is "Why didn't I do this a long time ago!" We now have a Macbook Pro (mine) and an iMac at home. What I need to know is how to make the dock move like a "wave". I doesn't really bother me, but my wife wants hers to move like it did on the store display.

I know it's probably very simple, but I'm probably just over looking the obvious.

Thanks in advance.