No, submarines cannot effectively hide from sonar by simply submerging at the bottom of the ocean floor. While it is true that the immense pressure at the bottom of the ocean inhibits sound transmission to some extent, sound can still propagate through water even at extreme depths.
Sonar systems used by submarines and other vessels operate by emitting sound waves and listening for their reflections. These sound waves can travel through water, including the depths of the ocean. The speed of sound in water is significantly faster than in air, and although it does decrease with increasing pressure, it can still propagate through the depths of the ocean.
Moreover, modern sonar systems are highly advanced and can detect and analyze even faint echoes or signals. They are designed to overcome various acoustic challenges, including the attenuation of sound waves due to pressure and other factors.
Additionally, submarines are not limited to hiding solely on the ocean floor. They have the ability to maneuver at various depths and distances from the floor, making it more difficult for them to be detected and tracked.
Therefore, while the pressure at the bottom of the ocean does affect the transmission of sound, it does not render submarines invisible to sonar. Submarines employ various other stealth techniques, such as using quiet propulsion systems, minimizing their acoustic signature, and employing tactics to avoid detection.