For a seriously strong foam adhesive, I use Liquid Nails Interior Projects Construction Adhesive.
However, for gluing cork roadbed to foam and gluing track to the cork, I use the least expensive generic latex caulk I can find at Wal-Mart. I save the Liquid Nails for jobs where greater holding power is desirable.
Oh, and I occasionally use foam-safe CA for certain jobs as well.
I have not created any water features yet, so I can't advise about the sealant.
- Jeff