Different types of waves? What is the difference between the wave produced in water when a rain drop hits  its surface and the wave produced when a source of sound is around it and wave from the source is transmitted from air to water?
 A: Sound wave in liquids is a longitudinal compression wave. The speed of such wave is expressed as $v=\sqrt \frac K \rho$, where $K$ is the bulk modulus of a liquid and $\rho$ is its density.
The bulk modulus indicates how much the liquid resists compression. Since water is not particularly compressible, the speed of sound in water is pretty high, about $1450m/s$ - substantially higher than the speed of sound in air, about $340m/s$, despite the fact that air has much lower density. 
Unlike a longitudinal compression wave, which involves tiny vibrations of molecules, the ripples produced by a rain drop, involve movement of water on macro level and have completely different propagation mode - surface waves. 
Surface waves are pretty complicated: they are neither longitudinal, nor transverse, but rather circular: the individual molecules near to the surface undergo close to circular movements. 
The speed of circular wave depends on a number of factors, including the wavelength, but, in general, it is at least two orders of magnitude slower than the speed of sound in water.
To summarize, although both sound and ripples propagate as waves, they are based on very different physical mechanisms and have vastly different speeds.      
