Mari Bolte 
Submarines in Action [PDF ebook] 

Dive deep with the US military’s impressive submarines.Submarines move deep below the ocean’s surface, keeping an eye on other submarines and the ships that sail above them. These underwater warships can fire at enemies and break through thick layers of ice. Discover how these high-tech machines operate underwater for months at a time and learn more about the powerful weapons they use to keep the seas safe and why they are so important to the military.