In order to find the refractive index of glass wrt water, we need to multiple refractive index of glass wrt air into refractive index of air wrt water.
Refractive index of glass wrt air = 3/2
Refractive index of air wrt water = 1/(refractive index of water wrt air)= 3/4
so, Refractive index of glass wrt water = 9/8