You can use a shader which is the representation of the following expression:

sin(20* sqrt(sqr(2u - 1) + sqr(2v - 1)))

If you want more ripples you can increase the 20 to
a higher value.

This wave, however, is not perfect since its amplitude
remains constant with increasing distance wereas a real
wave decreases.

I hope you can use it for something usefull.

Ernst