This article describes a computational project designed for undergraduate students as an introduction to mathematical modeling. Students use an ordinary differential equation to describe fish weight and assume the instantaneous growth rate depends on the concentration of dissolved oxygen. Published laboratory experiments suggest that continuous exposure to low concentrations of dissolved oxygen (DO < 6.0 mg/l) causes a reduction in the average growth rate of summer flounder, compared with the conditions growth rates in normoxia (DO = 6.0 mg/l). Students use data from these laboratory experiments to estimate parameters in the fish growth model. Subsequently, students answer biological questions using their calibrated model. Analyses and simulations may be carried out in "Matlab," "R", or "Excel." "Supplemental materials are available for this article. Go to the publisher's online edition of 'PRIMUS' to view the supplemental file."