FactSentinel

Sound travels about four to five times faster through water than through air. At room temperature, sound moves through air at roughly 343 meters per second, while in freshwater it travels at around 1,480 meters per second. In seawater the speed is slightly higher, often about 1,500 meters per second, depending on temperature, salinity, and pressure.

The reason lies in how sound moves. Sound is a mechanical wave, meaning it passes from one particle to the next as molecules push against their neighbors. The speed of that wave depends mainly on how stiff the medium is (its resistance to compression) and on its density. Water is far harder to compress than air, and this stiffness outweighs the fact that water is also much denser. The result is that vibrations are passed along more quickly. In air, molecules are widely spaced and the medium compresses easily, so the disturbance moves more slowly. These values have been measured repeatedly and form the basis of technologies such as sonar and underwater acoustic mapping.

A common misconception is that denser materials always carry sound more slowly because they are "heavier." Density does slow a wave, but stiffness has a stronger effect, which is why sound travels even faster in solids like steel, at roughly 5,000 meters per second. Another mistaken belief is that sound is louder underwater simply because it is faster. Speed and loudness are separate properties, and sound intensity underwater is perceived differently because of how energy transfers between water, air, and the human ear.