Like this?
Funny I just saw this post. I spent most of yesterday figuring out how I was gonna make one work.
construction:
The metal rings are func_details. The bolts are func_brushes (so they don't cut the metal rings into a thousand polys and they have no physics)
The wiremesh is a displacement.
The glass tubes are 2 layers of green glass displacement tubes.
The area around the glass IS NOT WATER. It is an enclosed cube of black tex. I suppose I will make a black fade overlay to fade the bricks of the walls out fast.
Then the water from the top side will be in a seperate box of it's own. The water wont be swimmable and the tubes wont be seen from the top side.
problems (aka why the black box instead of water):
TF2 is weird with water and I haven't played with it much. But it seems anything in the same 'box' as water below the surface of water, even if in air space has an effect on the player.
Demos stickies and pipe bombs travel through the air slow as if they are in water.
But if the tunnels are in a box under the water box this doesn't happen.
Also, the water surface doesn't work if you are in air space under the water. It'll just be a flat green/grey color. But if you no clip up into the water it's normal. Then you can go back down to airspace and it will look right until you move the camera around (possibly looking into a new leaf) at which time the water surface is messed up again.
So I figured I'd just make it look really dark and add the second layer of glass which helps to block view some and gives it an underwater effect.
I'm interested to see if you get different results.