The refraction of light in water can be seen as the laser beam leaves the water. 3 different-coloured lasers show that the magnitude of refraction is a function of wavelength.

Referring to the amount of bending of the incoming laser, we can use Snell's law, which is used to describe the relationship between the angle of incidence and refraction
For detail about Snell's law : wiki page

The laser is mounted on an arm that can be rotated and locked into position. By altering the angle at which the laser enters the water, the angle of refraction can be shown. The laser can even be set to show internal reflection.

Could be used with other liquids, as long as they are easy to clean out.