Exactly one of my ideas back in the 70's!
Never tried it.
I hear you suggesting:
Glass
water
Glass painted black.
I think you can skip the metal. The metal is used to transfer the heat to the pipe, here the glass is the pipe, thus no need for the metal.
Might work. Water should not be allowed to get too hot.
In other words, make sure you have water flow.
How are you going to seal the edges, water tight?
If you live in a cold climate then may need another glass layer on top to insulate the panel and some insulation under it and edges.
Warm climate, might not need anything. It's hot already!
Remember you can't pressurize this glass sandwich, not even a couple pounds, 1 psi * 4 x 8 = 32 pounds lifting the glass up!
If it was this easy, I know of another that had this same idea. Nobody I know has tried it. You would think if two, now three people had this idea, then others would have had, somebody would have tried it. I conclude it must not work.
But, that said, I don't know why. Would love to know if this works. Or why not.
I just remembered a problem, this only applies to the insulation glass panel (third or top one). Most glass has iron (or is it lead?), which blocks the sun somewhat, Not recommended to put over solar cells. Here, the glass is part of the pipe, so no problem for the lower two layers.
Have fun!