It is actually an established fact that sound travels faster in water than in the air, but the statement that sound travels faster in the ocean requires further discussion, for there are a number of factors to consider before the statement can be backed with numbers.
When it comes to determining the speed of sound in the sea, calculations become quite complicated, for there are a number of factors that influence the outcome. Water pressure, salinity and temperature are factors that need to be taken into consideration when determining the speed of sound in the ocean. This also means that the speed will vary from one place to the other and the measurements will also vary depending on the season, time of the day, as well as the depth of the water at which the experiment is carried out.
The speed of sound in water changes with the increase of the salinity, pressure and temperature of the water. This means that speed measured close to the surface is higher than the speed measured in deeper layers. The surface of the water is warmed directly by the rays of the sun, and therefore it is always warmer than deeper layers. The deeper you dive into the water of the ocean, the colder it becomes, which will cause the sound to slow down, but temperature decreases only up to a certain depth – after that threshold, temperature stays constant. However, the speed of sound will keep changing. Even though temperature does not change any longer, there is another powerful factor that influences the speed of sound, and that is pressure. The pressure of the water becomes higher with depth, and so does the speed of sound. The third factor, salinity, does not have such a dramatic effect on the speed of sound, for the simple reason that salinity variations in the ocean are not very significant.
To give you a general idea, we can say that the speed of sound is 340 m/s in the air and almost five times as much, 1,500 m/s, in water. The salinity, pressure and temperature profiles of the water further influence the speed, creating an area of minimum speed at around 1,000 meter depths. This phenomenon creates a so-called sound channel, which concentrates the sound waves, thus making it possible for them to cover large areas underwater.
The science that examines the speed of sound propagation in marine environments is called underwater acoustics. The findings of scientists are then used for developing detection and communication technologies such as sonars, acoustic telemetry, underwater navigation, even seismic exploration, marine biology and the study of the climate. All in all, remember that sound travels faster in the ocean than it does through air, indeed; but how fast it gets depends on many factors and requires complex calculations – calculations that are highly important for furthering science and our knowledge of the sea.