Sand walls can collapse suddenly, especially when water levels change (like, with the tide). If you make too deep of a hole, you can find yourself buried with little warning. Knee-deep is a good height that even if it does collapse in you, you’ll still be able too get yourself out. Hip-deep, you might end up stuck as the wet sand keeps filling up as fast as you can dig it out.
What happens when the depth of the hole exceeds the height of the knees
Sand walls can collapse suddenly, especially when water levels change (like, with the tide). If you make too deep of a hole, you can find yourself buried with little warning. Knee-deep is a good height that even if it does collapse in you, you’ll still be able too get yourself out. Hip-deep, you might end up stuck as the wet sand keeps filling up as fast as you can dig it out.
What I’m hearing is to dig a waist size hole, and then shove your little brother in there.