How do I carve sand? (No, not with teeny, tiny tools!)

Newbie, hope I am in the right place! I have carved a platypus swimming through a wall of water and would like to make a base that looks like sand... but have no idea how to! Is there a place on the forum I should look or do I just ask here like I have?

platypus.jpg

Attached Images

• platypus.jpg (59.5 KB)