Good info, poor organization
The "underwater warfare" covered by this book is mostly mines (torpedoes). There is a lot of information on technology and personalities, but the narrative jumps back and forth in time and among personalities. There are also a few chapters on the development of submarines, leading up to the Hunley, but this topic is covered much better in Chaffin, "The H.L. Hunley" and Ragan, "Union and Confederate Submarine Warfare."