Sound travels over four times faster in water than in air.
Why it is true
Water molecules are closer together, which facilitates the rapid transmission of sound waves between them.
Source: Acoustics Dept
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.