Bill Parker wrote:
We are putting in a small pond with waterfall/stream. All the literature
that I have read recommends sealing stone in the stream with a foam. Every
foam product that I can find says to not use under water. What kind of foam
are they talking about.

I used Great Stuff and really regretted it. It makes a mess, never
comes off the rock and as far as I can tell, never worked worth a damn.
It is however what everyone uses. I agree with the other poster that
you really want a proper lining under your waterfall and good placement
of the rocks so that you just don't need it.