How can a science concept be taught in a way that generates interest, gives students the opportunity to consider other possibilities, does not lock them into one way of doing or seeing things, and gives them some ownership of their learning? These authors searched high and low for the perfect activity to illustrate a key concept for their partner teacher's fourth-grade classes: how depth affects water pressure. Unfortunately, the concept was so obvious that the students were not even curious. This classroom experience was an endpoint, but it should have been the beginning of a more complete investigation leading to better understanding of the topic. What the authors were seeking was a way to provide students with inquiry activities that encouraged them to identify and solve problems. Specifically, students needed a structure for problem-solving that was flexible enough to promote ownership of the process, which in turn, would lead to better understanding of the underlying concepts. To transform this activity into a real inquiry investigation, they included in their demonstration one variable--volume--that is commonly thought to affect water pressure, and not just the variable that actually affects water pressure--depth. With two variables, students had to use inquiry to determine which variable really matters. (Contains 3 figures.)