Answer:
What English word has three consecutive double letters?
Has feathers but can't fly. Rests on legs but can't walk.
Come up and let us go. Go down and here we stay.
What can be swallowed, but can swallow you?
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.
Break me and I am better immediately set and harder to be broken again.