Modern submarines are engineering marvels. Most people only know about submarines by what they have seen in movies or television. Most movies show submarines back in World War II. There is almost no comparison of a modern submarine compared to an early 1940s submarine. Submarines are equipped with two types of sonar. They are passive and active. Passive is where a submarine listens for noise and begins to triangulate a bearing to that noise source. Active is where a submarine emits a burst of noise and listens for an echo return. World War II submarines were active, while a modern ...