You could also achieve this with a diffuse map and a refraction map. The method above is nicer but this is an option.
Diffuse map in diffuse slot.
Reflection 1.0
Glossiness 1.0
Refraction map in refraction slot (you may need to invert it, im not sure)
Refraction glossiness 1.0
You could also put the refraction map into the absorbtion slot and set the colour to a light blue and turn the distance up.