Submarine

The primary defense of a submarine lies in its ability to remain concealed in the depths of the ocean. Early submarines could be detected underwater by the sound they made. Water is an excellent conductor of sound, and submarines can detect and track comparatively noisy surface ships from long distances. Modern submarines are built with an emphasis on stealth. Advanced propeller designs, extensive sound-reducing insulation, and special machinery allow a submarine to be as quiet as ambient ocean noise, making them extremely difficult to detect. It takes specialized technology to find and attack modern submarines. This submarine in particular might not be so stealthy.