What constitutes a playmate? Tom's been wondering about this since a recent trip to the ocean where his grandchildren played tag with waves. The discussion reminds us of other reliable playmates such as puddles, streams, and sticks. Ross points out that these playmates can meet children's seemingly insatiable need for play--the ocean will never be too tired to play tag. They are also emotionally neutral. There's no point in engaging in a power struggle with a wave.