"I come once in a minute, twice in a moment, but never in a thousand years. What am I?"

I am lighter than a feather yet I carry millions of tonnes. I have no shape yet I take every shape. I float even though I am enormously heavy. What am I?

I am the daughter of water yet when water touches me I die. What am I?

I am dug for the living yet filled by the dead. I cost everything but give nothing back. What am I?