I'm not fully aware of what I can or can't do with GSC, perhaps it's possible to delete and create brushes?

Make it a script brush and apply the water clip texture

I tried this, and it did not work. Also, you can't link a regular brush with anything.
Maybe it's not possible and Treya...

link them?

or just move them both?

I'll try linking them right now, but the clip_water brush would need a targetname to move (as far as I'm aware) but when selected the E...

But since the water is moving, how can I ensure the clip_water brush will follow? I'll try to use the wave brush a little more and see what I can do.

I just went and messed around a bit more, and it seems like I got further than I ever have with the clip generation tools, but all it could do was create solid clips. Interestingly, zombies can't move when they're in the water (not the solid clip, just water) but nothing changes about the ...

I have not done anything with KVPs, which I have a feeling has something to do with the answer.