Sound travels much faster and often farther in water than in air: typical values are about 343 m/s in air at 20 °C and around 1,484 m/s in seawater under typical surface conditions, meaning sound moves roughly four times faster underwater.
Overview
The speed at which sound waves propagate depends on how easily vibrations move through a medium. Water’s molecules are closer together and more strongly coupled than the molecules in air, so pressure disturbances travel more efficiently and with less compressional delay, producing substantially higher propagation speeds in liquids compared with gases.
Factors affecting speed
Several physical factors change the exact speed of sound in water and air. In air the speed depends strongly on temperature and to a lesser extent on humidity and pressure. In water the speed depends on temperature, salinity and depth (pressure) so warmer, saltier or deeper water usually transmits sound faster than cold, fresh surface water.
Practical implications
Because sound moves faster and can travel long distances with less attenuation in water, marine animals and human technologies exploit it for communication and sensing. Whales and dolphins use low-frequency calls to communicate across hundreds of kilometres, and sonar systems rely on predictable underwater sound speeds for navigation, mapping and object detection.
Quick related facts
- Air speed (typical): ~343 m/s at 20 °C
- Water speed (typical): ~1,484 m/s in seawater
- Main reason: closer molecular spacing and stronger coupling in liquids
- Variables: temperature; salinity; pressure