Hi, I'll make this quick:

I have shallow water in a map, as well as paint. The problem I'm having is that the surface under the shallow water can be painted. I need it to not be so. I also have deep water in the map, and it doesn't have the same issue. I tried putting a paint cleanser brush along the surface of the shallow water, going down to the surface under the water. No luck, but it does clean physics objects (useless for me). I'm wondering if I can have some kind of clip, that stops gel blobs, but doesn't collide with players. Or maybe a way to make the texture unpaintable...

Any suggestions would help!

There's really no way to block gel blobs. What you could do is change the floor texture to toolsblack (it doesn't accept paint), then add a 1 unit thick func_brush on top with the floor texture. Set it to non-solid, and then the paint won't affect the floor texture. You might want to move both floors down 1 unit if you want the new floor to be flush.

That's a good idea. But I do not want the gel to look like it is going through the water and the floor under it. However if I were to do that idea I would make a non-solid brush and a playerclip over it. It doesn't really work for my map.

Set up some sprayers above the water with all the effects turned off and the gel type set to erase.

Well I just discovered something. Paint cleansers apparently do not work when flush with a water surface. Problem solved.

You could use a texture at the bottom of your pool that simply doesn't accept paint: look into its .VMT and make sure it has a line with the following parameter:

"%nopaint" 1

(Sorry but I can't remember one to recommend right now)

Or create a custom texture with that parameter inside

Thanks for that info for the future, but for now the problems solved