I'm trying to create a bullett time effect with water, and for the most part I've got everything working the way I want. However, I'm trying to add some refraction to my water, but whenever I turn it on in the shader, my whole object goes opaque. Is there a trick to getting refraction to work? I'm sure it's something simple, but I can't find it. Yes, I have raytracing turned on in the render globals.

Thanks.