You may not think of engineering and squirt guns in the same sentence. However, like many examples of engineering design, the squirt gun pump mechanism is uncomplicated, yet elegant, and very inexpensive to manufacture. The design is widely used because of its simplicity and low cost. With only a few moving parts, it is able to deliver a stream of water, a spray of cleanser, or a squirt of liquid soap. In this article, the authors will examine how these simple, everyday pumps operate. In addition, a lesson is included, which follows the 5E Learning Cycle Model. (Contains 4 figures.)