about that cube portal...
I found that if you build and add a cube (or any other shape, I assume) you can put a sheet on the bottom of that shape and intersect it. I know one should not normaly intersect sheets, but it does wrap the sheet around the edges of the cube. I did this and capped off the top and bottom, thusly creating a nifty little "box" of water. I think that's the effect you were going for. Let me know if I'm doing this the long way, but it seems a lot simpler than building a bunch of individual sheets.
