Answer:
I am used when you jump off a bridge for fun.
I drift forever with the current and flows to your everyday life. I make living easy but I am good at killing people too.
Deep, deep, do they go. Spreading out as they go. Never needing any air. They are sometimes as fine as hair.
I am a mountain at night, meadow at day. What am I?
My teeth help me suck.
Runs over fields and woods all day. Under the bed at night sits not alone, With long tongue hanging out, Resting at your feet until we go for a walk