While students were constructing the concept of rates of change, linear relationships, and nonlinear relationships in a first-year algebra class, the wanted to build a task that allowed them to increase their understanding of covariation, that is, how two variables change in relation to each other. Research has shown that students who have built an understanding of covariance are more successful at learning more advanced mathematical concepts (Thompson 2017). Additionally, the authors wanted to find an activity that excited students so they would engage in vigorous mathematical discourse both in small groups and as a whole class. Their students had a large range of mathematical abilities, so they needed an activity that provided challenging opportunities for all of them. What they presented was an activity that focused on filling three-dimensional letters of the alphabet with water, which met all of these goals.