Great Stuff Marine Safe?

[Devilish]

Need to create a rock to hold my shelf piece of lr. Was thinking of creating a 4 legged pvc structure and then resting the shelf on top. Don't want the "legs" showing so thought of spraying them with Great Stuff, the canned foam, and dipping in some sand. This should give them some good texture and shape. Not sure if the foam is safe though.

[ebola]

I think the concern would be that it would soak up water and possibly dissolve. A better idea might be letting it dry, hitting it with a couple coats of Krylon Fusion, and then maybe on the last coat of paint, sprinkling sand over it then. That way it would be completely waterproof and have that textured look you want.