Answer:
A precious stone, as clear as diamond. Seek it out while the sun's near the horizon. Though you can walk on water with its power, try to keep it, and it'll vanish in an hour.
You eat something you neither plant nor plow. It is the son of water, but if water touches it, it dies.
Looks like water, but it's heat. Sits on sand, lays on concrete. A play on the eyes, but it's all lies.
What can't you see, hear or feel, until its too late. What shadows love, and shopkeepers hate?
What covers its face with its hands, speaks no language, yet most known what it's saying?
I repeat only the last word you say. The more I repeat, the softer I got. I cannot be seen but can be heard. What am I?