Here's a crude analogy of hole flow. Think of a variation of "musical chairs" in which there is one too many chairs. A bunch of players and a bunch + 1 of chairs, players sitting in all but one chair. Frequently someone gets up and moves to another chair, then someone else does the same, and so on. There's always a minimum of one empty chair. The empty chair does not move, but from a distance the empty spot appears to move in opposition to the actual movement of the players.
