Studies show that overall seafood consumption in the United States is rising (Agriculture and Agri-Food Canada 2012). Other research estimates that as much as 40% of the seafood caught worldwide is discarded, while countless sharks, whales, dolphins, birds, sea turtles, and other animals are unintentionally killed or injured by fishing gear (Kledjian et al. 2014). This capture of non-targeted species--known as bycatch--is a worldwide challenge to maintaining sustainable fisheries and protecting endangered species. In this activity, students use a simple classroom model to design and test solutions to bycatch in the tuna fishery. They collect and use data to optimize their design and consider how their model might look in real life. The lessons we tested in a high school marine science course, but it could be adapted to an environmental science or biology course from eighth grade up. After this lesson, students should be able to: (1) discuss the need for sustainable fishing in the world's oceans; (2) design, evaluate, and refine a solution for reducing bycatch; and (3) relate their model design to real life. The activity takes 90-100 minutes as written--less if background reading is done as homework or more if discussion of the reading or data analysis is extended or if students do deeper research of real-life bycatch reduction strategies. Students should work in groups of four. The authors had good results blending students who have diverse talents and skill levels.