This lecture is designed for lifelong learners with a general interest in submarines and their role in U.S. national defense. Discussion, complemented by photography, will include a brief history of submarine development. We will explore how these vessels operate at sea for extended periods very independent of an external life-support system. We will also cover their operational and environmental capabilities and their importance for our national defense. Non-technical in content, this class requires little to no understanding of the scientific or technical aspects of ship design or operation.