Sailboats use their engines to charge their batteries, but engines are loud and defeat the purpose of sailing. There are alternative energy systems on the market that use wind, sun, and water to charge the battery, but none that just use tidal energy. This project set out to design and build an underwater turbine that can be used to charge a sailboat’s 12V deep-cycle battery while it is moored or anchored. The design includes the selection and testing of a remanufactured car alternator as the power generating system and the design of the turbine to alternator coupling. The turbine blade shape was calculated using a general rotor design procedure described in Wind Energy Explained. The Buckingham Pi Theorem was applied so a non-dimensional equation could be used to scale a model of the blades; the scaled model was tested in the wind tunnel at Union College. From those tests, it was concluded that the blade shape would not produce enough power, while meeting the project constraints, in its application to sufficiently charge a sailboat’s battery. With more time and research, a more efficient blade could be designed to produce the desired power and a complete product could be manufactured.