A study of the effect of science teaching with a multimedia simulation on water quality, the "River of Life," on the science conceptual understanding of students (N = 83) in an undergraduate science education (K-9) course is reported. Teaching reality-based meaningful science is strongly recommended by the National Science Education Standards (National Research Council, 1996). Water quality provides an information-rich context for relating classroom science to real-world situations impacting the environment, and will help to improve student understanding of science (Kumar, 2005a; Kumar and Chubin, 2000). The topics addressed were classes of organisms that form river ecosystem, dissolved oxygen, macroinvertebrates, composition of air, and graph reading skills. Paired t-test of pre- and post-tests, and pre- and delayed post-tests showed significant (p less than 0.05) gains. The simulation had a significant effect on the conceptual understanding of students enrolled in a K-9 science education course for prospective teachers in the following areas: composition of air, macroinvertebrates, dissolved oxygen, classes of organisms that form a river ecosystem, and graph reading skills. The gain was more in the former four areas than the latter one. A paired t-test of pre- and delayed post-tests showed significant (p less than 0.05) gains in the water quality and near transfer subsets than the dissolved oxygen subset. Additionally students were able to transfer knowledge acquired from the multimedia simulation on more than one concept into teachable stand-alone lesson plans.