water
As clear as a bell.
. Simile
The simile "as clear as glass" means something is easily understood or transparent, just like how clear glass allows you to see through it without obstruction. It is often used to describe a situation or concept that is easy to grasp or perceive.
waka waka aye aye
A simile.
The simile is usually stated "crystal clear". Crystal is fine glassware, very clear and sparkling. Thus, when something is "crystal clear", it would be like seeing something through the clear glass of crystal.
Yes, "as plain as the nose on one's face" is an idiomatic expression. It means that something is very clear or obvious.
The roof was a weak as a dried up leaf. The desert sun burnt like fire. The HD-TV was clear as spring water.
her voice was more high, clear and beautiful than the song of a bird crying to the rising sun.
A metaphor
It is a simile.