The laws of reflection or refraction are the same for sound as for light. The index of refraction of a medium (for sound) is defind as the ratio of the speed of sound in air `343 m//s` to the speed of sound in the medium.
What is the index of refraction (for sound) of water `(v=1498 m//s)`?
What is the critical angle `theta`, for total reflection of sound from water?