Why does sound travel faster in water than in air?

Does it have to do with it being a longitudinal wave? Or does it need an entirely different index of refraction?
I'm really confused because when I used an equation from a textbook and compared sound in air to water, the speed of sound in air was faster than it in water.

If you're comparing the speed of sound in water vs in air, it all has to do with the greater density of water. The molecules are closer together in water, and so sound waves (which are longitudinal) can travel faster.

Don't even think about refraction here. Refraction of sound isn't in play when you are talking about sound just traveling through one consistant medium. If you had water changing depths or temperature, or if the sound traveled through water and then through air, then you'd have to consider refraction.

Consider sound as a man S. Now let's assume S has two options to get to his desired destination X. In a state of air, which we will consider 4 cabs spaced far apart, it will take S longer to get from one car to the next to get to his destination X. However in a liquid or solid state, where the 4 cabs are much closer together and therefore easier to reach he is able to get to destination X faster. This type of definition is not concrete, but generally because sound requires a medium to travel the closer the medium is the faster sound can travel through that medium before diminishing. Sound vibrates matter and is an effect of vibration of matter, the closer the matter is the more effective the vibrations are.

B'coz water is more denser then air.

I don't know what equation they gave you in your physics class but the expression for the speed of a longitudinal wave we have for speed of sound in a fluid is v = sqrt(B/p), where B is the bulk modulus and p is the density of the fluid. Although water is more dense than air (density,p, of water = 1 x 10 ^3 kg/m^3), the compressibility of water (corresponding to bulk modulus) is much greater than that of air (approx 2.2 x 10^13). Therefore the speed of sound in water is 1480 m/s at 20 deg. C vs. the speed of sound in air, which is 344 m/s at 20 deg.