Answer:
It happens when something has been cut with H2O.
What type of bar gets you wet walking in and out of it but keeps you dry inside?
A hill full, a hole full, yet you cannot catch a bowl full.
When I get closer my tail grows longer, but when I go away my tail leads the way.
I march before armies, a thousand salute me. My fall can bring victory, but no one would shoot me. The wind is my lover, one-Βlegged am I. Name me and see me at home in the sky.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.