Hidden Sand Hole

When you are at the beach, pick a victim or friend that is lying down on a towel on the sand.

When they get up to use the restroom or for a drink, remove the towel and dig a hole where the towel sits.

Put back the towel in exactly the same place so the victim don't suspect anything. When the victim lays back down on the towel their ass will fall in the hole! The deeper the hole the better!