An acoustic map of underwater seismic activity of the U.S. Pacific Coast. NOAA uses the U.S. Navy's worldwide underwater sound monitoring system to map earthquakes and other seismic activity along the ocean floor.
Some people may think that because it is easier to hear in air than in water, then sound must travel faster in air. Actually, sound travels about 4.3 times faster in water than in air.
The reason it is harder for humans to hear in water is because there are two different ways we hear: through air conductivity or vibrations in the audio bones from our inner ear, and through bone conductivity or vibrations in our skull. Bone conductivity is used to hear under water, but it is 40 percent less effective than air conductivity.
It is also harder to hear under water because when the outer portion of our ears fill up with water, the eardrums can’t vibrate.