The Submarine School, Submarine Base, New London, Connecticut, and other activities of Submarines Atlantic Fleet, have collaborated in the preparation of this manual. It is designed to serve as both an instruction and an operation manual. Since, in wartime, changes in design and construction developed rapidly as a result of battle experience, it became increasingly difficult to incorporate into this text all classes of submarines. Therefore, the USS Perch, or SS313, was selected as representative of the class discussed and described in the text. In some instances, however, it was found desirable to make reference to later units and to describe and illustrate these newer installations so that a more complete text would result. This book does not have all of the line drawings included and is printed in black and white.