The inspiration behind Katahdin was Rear Admiral Daniel Ammen, an advocate of a coast defense navy. Ammen was impressed by the British torpedo ram HMS Polyphemus. Unlike Polyphemus, which was primarily a torpedo boat, with ramming a secondary function, the American design was for a pure ram, with no torpedoes carried. Katahdin's design was a new departure in naval architecture, built to ride extremely low in the water with her bow awash while under way. Her hull embodied several new features later used in early submarines.