The Little GMod Water Problem

Yes, even someone, who's creating tons of GMod images, needs some help.

Here is my problem:
If you can see, the prop is underwater. Beneath the water surface. But something is wrong. You can see it submerged and not submerged. That's weird. Normally it should be completely distorted by the material. But it seems to be twice here. One completely behind that material and one nearly unaffected by the material. I hope you know what I exactly mean.

I'm pretty sure that I'm not the only GMod player that encountered this problem. Is there any way to fix this? Thanks in advance.