What adhesive do you suggest I use to adhere rocks to a pond liner?

Silicone. The ge brand. Nothing works like it and it will stay stuck in the water. I just did this myself with LOTS of trial and error. I used a dab of hot glue on the bottom edge of each rock so (so you can't see it, when it dries it looks cloudy) just to hold the rock up until the silicone set. The hot glue alone will not work. I tried that too

I agree with Rachel's great advice! I use silicone (in a caulk gun) but never thought to use the hot glue as a temporary step till the silicone dries. Thanks Rachel!

Thanks!

If you are going to have fish in there, make sure whatever you use is safe for them. Good tip on the hot glue!

You should check out the product RockToRubber.