Using simple laboratory gear, students can simulate the stratification properties of a freshwater lake and the impact of salt on the relationship between temperature and density. Because some students have little or no intuition for different thermal stratification regimes, this activity is designed to focus on this fundamental behavior of freshwater lakes. The experiment exposes students to basic data collection, analysis, and visualization techniques using an inexpensive, commercially available data logger and sensors. It can be used as motivation for a discussion of sampling techniques, such as sampling density and sampling rate, and how choosing among them can influence the reliability of an experiment’s results.