Answer:
You heard me before, yet you hear me again, then I die. Until you call me again.
They can be harbored, but few hold water. You can nurse them, but only by holding them against someone else. You can carry them, but not with your arms. You can bury them, but not in the earth.
To cross the water I'm the way, for water I'm above. I touch it not and, truth to say, I neither swim nor move.
What comes once in a minute, twice in a moment, but never in a thousand years?
What has a big mouth, yet never speaks?
It weighs next to nothing but no one can hold it for long. What is it?