A descriptive account of the conception, design, and wartime employment of large flying-boats, detailing hull and engine features, crew complement, and the evolution from earlier float seaplanes. It outlines patrol patterns and wireless navigation methods used to detect and attack enemy submarines, and recounts episodic missions—sightings, bombing attacks, reconnaissance, and rescues—illustrated by charts and photographs. The narrative emphasizes technical challenges, innovation in construction and tactics, and operational life at a coastal air station, and concludes by contemplating peacetime applications of enlarged flying-boats for carrying mail and passengers over sea routes.