My honey Gino does just that pondmaster. He uses the effect to make an artwork look old. But, he uses Elmers yellow glue to get that effect. Using white glue makes the sand more of it's original color.
however, with you dealing with water, you may want to smear a thin layer of pond-safe silicone glue instead, and throw the sand into it, then patting it in. It does look beautiful, at least on the sculptures Gino has done this too. :)
Nicci

Here is a link that might be useful: sculpture...the white piece at top photographed before the sand

Wow! Very impressive!

I think I will go through with my plan on the sand, adding maybe some gravel and dirt too. D you know of any waterproof spray on glues? That would be much easier than something that could be spread on. I will admit, cheapness is the issue here, but just because there is ALOT of liner to cover!

Ive been thinking about this. You will have to check about the effects of water cause that I am not sure of. You can get spray foam spray((DAP) (almost the same a waterfall foam but much cheaper) As it starts to kick (harden) you can apply anything you want to the top of it. Sand, dirt, peat, pea gravel.

The best way to do it is 2 part expanding foam that you mix by hand. You can add powdered tempera paint to it as you mix to change the color of the foam. Then as it kicks you can add other stuff on the surface.

This would insure that the under laying foam was not standing out as yellow. Plus the foam is not UV stable and will break down if not covered.

I use this all the time is my business but it is not in direct contact with water.

Thanks! Do you think I should put the liner in place first, then do this? How much do you think that would run 9or really I guess how much is in a can), and could I get at a home depot type place?

Back in my model railroading days I used to glue down sand or gravel (and lots of other things) with something called "acrylic matt medium," which is just acrylic paint with no pigments. It looks milky white when in the can but dries fairly clear (and not shiny, that's the 'matt' part) when used as a glue. Any good art supply store should have some.

You can cut it with water so its not as thick, and add a few drops of detergent to help it wet out the sand. Make sure you rinse it off good if you use the detergent. Spray it on the sand in place with an old pump spray bottle.

If you can get paint to stick to the liner then this should work for you.

Yeah home depot or lowes has it. Put the foam on thin because it really expands. And yes make sure your liner is in place when it fully sures it will be hard. It basically the same thing as waterfalls foam just dont colored black.

I think its about 4-5 a can.

It would be best to do this with the pond totally empty. Let it start to kick. You can spead this up by misting it with water. Just is the surface goes form super sticky to tacky throw our sand, dirt, pea gravel whatever on it.

Wear gloves because even acetone wont take this stuff off if you get it on your hands.