Small waterblock is invisible.

I am trying to make a small water block that is in a small hole. The dimensions are about 32x32. The water dissapears when I lower it into the hole. It doesn't matter if I use depth mask or not. If I make the hole a little larger then parts of the water are visible and others aren't Like there is a hole in the water.

How can I make a small hole with water using a waterblock?

Thanks,
Mark Harmon