The picture below illustrates both points well. First, the children are transporting the water into the bucket. Second, they are filling the bucket as full as they can and still being careful not to spill.
Those are important reasons why I build. Another important reason surfaced from reflections on a book I read this summer: a child's work; the IMPORTANCE of FANTASY PLAY by Vivian Gussin Paley. In the book, Paley talks about fantasy play as the children's agenda that spontaneously emerges between all the teacher-planned activities and projects. Her first teacher told the undergraduates that children in the nursery school where they were observing were the only age group that was constantly busy making their own work assignments. Because Paley provides the time and space and respect for children's fantasy play, she sees the children creating and recreating dramatic themes that span human history and that are reflected in the great works of literature and drama. She says: "Words, words, words, where do they all come from? It sounds like the poetry of a child's soul, nothing less, but the children are imagining vivid drama that must be acted out." (p. 32)
After reading the book, I began to construct a parallel between fantasy play and sand and water play. All the operations the children recreate in and around the sensory table span human history. I have often wondered why children dig, pour, fill, and transport as soon as they see the sand or water. Maybe the children are recreating those operations from a time when they were important to our very survival. Not only are they recreating those primary operations, but they are using contemporary implements to create new and novel operations. Those elemental operations must come out. (Additionally, those operations around the sensory table often lead to a good deal of fantasy play, especially with the older children.)
Below is just a sampling of those operations. Some operations involve just the hands and arms, and others use various implements. Some are straight forward and simple, and some are more complex.