When I disturb a body of water, what causes the familiar "water moving" sound?
If you throw a stone in a large body of water, this is what you should hear:
- a high pitched slapping sound when the stone makes contact with the water. This is due to the air between the stone and the water being pushed out, as well as the surface ripples
- a low pitched sound growing in pitch (like "Doo-eeeee" ;-) due to the stone sinking and leaving an air "hole" in the water in its trail; this is then filled gradually with water which makes the sound raise in pitch
- a bubbling sound due to air bubbles trapped under water by the stone, emerging.
- a random noise due to waves colliding on the surface of the water.
The major source of sound when water is disturbed is the creation of underwater air bubbles, which oscillate in shape and size, producing damped sinusoid sound waves. The resonant frequency of the bubble depends on its size, so many bubbles of different sizes and different resonant frequencies produce the "burbling" sound that we associate with water being disturbed.
As your question is very general, I can suggest a general answer: when a water wave is hitting a wall for example, you can "trap" an air bubble between the wave and the walls. This bubble can be compressed, the pressure will be higher and when the water moves, this bubble "explode" emitting a sound (which is nothing else than a pressure wave).
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.
Something(can be stone/ pebbles/ hands/ water etc.) interacting with water creates "oscillation of pressure". Nature of "oscillation of pressure" depends on both water and interacting substance. And mostly familiar things interact with water thus giving rise to the characteristic sounds.
From Sklivvz's answer: "a high pitched slapping sound when the stone makes contact with the water. This is due to the air between the stone and the water being pushed out, as well as the surface ripples"
I think the high-pitched sound is caused mainly by the breakdown of the tension formed by the water layer on the surface (see http://en.wikipedia.org/wiki/Surface_tension for more detail). So it's similar to slapping a table with your hand.
You would hear the sound with the mass of the stone brushing against the air, and the air above the water where the stone is falling into would push against it, creating a small air pocket that would make a slapping noise.