Final answer:
When a sound wave moves from water to air, it slows down due to the difference in density between the two mediums.
Step-by-step explanation:
When a sound wave moves from water to air, it slows down. Sound waves travel faster through liquids, like water, than through air, because water is denser than air.
The speed of sound can change when it travels from one medium to another, but the frequency usually remains the same. If the speed of sound changes and the frequency remains the same, then the wavelength must change.
In this case, when the sound wave moves from water to air, the greater speed of sound in water causes the wavelength to decrease, resulting in a slower speed when it enters the less dense air.