If you want them to stay put, dig a "V" shaped hole and get their ass down deep. Then spread their arms out some and have them put their hands down near the bottom of the hole away from their body. Then start filling in the hole, adding some water as you go so the sand will pack. Fill up the hole right up to their chin, making sure the sand is damp and pack if down firmly. Where their feet are showing, make sure they're spread apart some and the sand again is damp and packed. That should keep them from having any chance to escape so you can have your fun! 😝