Answer:
Round as an apple, deep as a cup, and all the kings' horses can't fill it up. What is it?
I'm tall in the morning and short in the noon. I disappear at night but I will be back soon.
The itsy bitsy teeny weeny yellow polka dot variety is quite popular.
I am nothing but holes tied to holes, yet am strong as iron.
I have a neck but no head. I have a body but no arm. I have a bottom but no leg.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.