Why are acoustic waves more useful than electromagnetic waves for finding submarines underwater?

Acoustic waves are significantly more effective than electromagnetic waves for detecting submarines underwater because seawater is highly opaque to electromagnetic radiation, which does not propagate well through the medium. In contrast, water is an excellent conductor of sound, making it far more transparent to acoustic waves than to light or other electromagnetic signals.12

Because electromagnetic waves are rapidly attenuated and absorbed in water, they are largely ineffective for long-range underwater detection. Acoustic waves, however, can travel over great distances, allowing for the use of sonar (sound navigation ranging) to locate submerged vessels. Sonar systems detect submarines either by intercepting the noise generated by the vessel (passive sonar) or by emitting sound pulses and analyzing the echoes that reflect off the submarine's hull (active sonar).3142

While acoustic detection is subject to challenges such as sound refraction caused by temperature and salinity gradients, it remains the primary method for underwater surveillance, as electromagnetic alternatives currently face extreme physical obstacles in the marine environment.125