Group dynamics have been a topic of interest and research that has puzzled generations and continues to captivate the experts. Twenty-five years ago, Irving Janis, professor of psychology at Yale, first presented his theory of groupthink. Janis introduced the term groupthink to refer to a mode of thinking that people engage in when they are deeply involved in a cohesive in-group, when the members striving for unanimity override their motivation to realistically appraise alternative courses of action (1972, 8). On 9 February 2001 Navy Commander Scott Waddle, Commanding Officer of the fast attack nuclear submarine USS Greeneville, ordered his boat to a depth of around 400 feet and directed an emergency blow maneuver. When the USS Greeneville broke the surface of the Pacific she collided with the Japanese fisheries training vessel, the Ehime Maru. The Ehime Maru sank within 45 seconds along with the souls of nine Japanese nationals. Commander Waddle and his crew were recognized as one of the best in the Pacific Fleet. What went wrong? This thesis explores the groupthink phemen and utilizes Janis' theory to come to the conclusion that groupthink was indeed present and was one of many causal factors of the accident.